Delphi Unit (tested on D7, should work on any version) that allows you to open, change, print and similar things on spread sheets using Excel, OpenOffice or LibreOffice in a transparent way: The code uses the app. you have installed or that better suits the file type you are using.

Most of the procedures in this object are dual: They behaves differently depending on the app. being used (Excel/OpenOffice/LibreOffice), but please note that some functions could not be implemented in one of the two apps.

// *******************************************************
// ** Delphi object for dual SpreadSheet managing using **
// ** Excel/OpenOffice/LibreOffice in a transparent way **
// ** By: Sergio Hernandez (oficina(at)hcsoft.net)      **
// ** Version 1.08 18-10-2013 (DDMMYYYY)                **
// ** Use it freely, change it, etc. at will.           **
// *******************************************************

//Latest version, questions, modifications:
//
// https://github.com/sergio-hcsoft/Delphi-SpreadSheets
// http://user.services.openoffice.org/en/forum/viewtopic.php?f=21&t=47644&p=219641
// http://forum.openoffice.org/en/forum/viewtopic.php?f=21&t=47644&p=288656#p219641

{EXAMPLE OF USE
  //Create object: We have two flavours:
  //(A) from an existing file...
  HCalc:= THojaCalc.create(OpenDialog.FileName, false);
  //(B) from a blank document...
  HCalc:= THojaCalc.create(thcOpenOffice, true); //OpenOffice doc if possible, please
  HCalc.FileName:= 'C:\MyNewDoc'; //Needs a file name before you SaveDoc!
  //--end of creation.
  HCalc.ActivateSheetByIndex(2); //Activate second sheet
  if HCalc.IsActiveSheetProtected then
    ShowMessage('2nd sheet of name "'+HCalc.ActiveSheetName+'" IS protected');
  //Change a cell value.
  IF HCalc.CellText[i,2] = '' THEN HCalc.CellText[i,2] := 'Hello world!';
  HCalc.AddNewSheet('New Sheet');
  HCalc.PrintDoc;
  HCalc.SaveDoc;
  HCalc.Free;
}

{TODO LIST:
  -PrintActiveSheet is not working for OpenOffice/LibreOffice (even possible?)
}

{CHANGE LOG:
 V1.08: (18-10-2013 DD/MM/YYY)
   ***************************
   ** By user MARCELVK from **
   ** forum.openoffice.org  **
   ***************************
   -SetTextCell in OpenOffice/LibreOfice case use .string not setFormula().
   -Added properties LastCol and LastRow to get the bounds of used cells.
 V1.07: (15-05-2013 DD/MM/YYYY)
   -From V1.03, trying to open Excel without Excel installed doesn't try to open
   OO instead, just raise an error. Fixed in create().
 V1.06: (08-04-2013 DD/MM/YYYY)
   *******************
   ** Joseph Gordon **
   *******************
   -New function Orientation(row, Col, Angle) to rotate the text in a cell.
   -Auto adjust a column's width using AutoFit(col)
 V1.05: (22-02-2013 DDMMYYYY)
   -Restored "$INCLUDE Compilers.inc" from V1.03 so code is suitable for other
   versions of delphi (Philipe did this works, I just deleted this line ;-).
   -Restored 3 commented lines with params. for a code formatter Philipe use. It
   has no use for others don't using formatters, but it won't harm us!
 V1.04:
   -New function StillConnectedToApp() to check if user closed app. manually.
   Note: Useful for previewing doc. in OO using code like this:
   //
   HCalc.Visible:= true;
   if HCalc.IsExcel then begin
     //Preview of all sheets, one after the user closes the other...
     for i:= 1 to HCalc.Document.Sheets.count do
       HCalc.Document.Sheets[i].PrintOut(,,,true);
   end else begin
     //ooDispatcher is just a variant
     ooDispatcher:= HCalc.Programa.createInstance('com.sun.star.frame.DispatchHelper');
     ooDispatcher.executeDispatch(HCalc.Document.getCurrentController.getFrame, '.uno:PrintPreview', '', 0, VarArrayCreate([0, -1], varVariant));
     //OO returns control just after showing, while excel waits for user to close it.
     //If you don't wait for user to close preview, you will see just a flash:
     while HCalc.StillConnectedToApp() do
       sleep(1000);
     //User has manually closed the preview window at this point.
   end;
   //
 V1.03:
   *****************************
   ** Van Coppenolle Philippe **
   *****************************
   -Reformated code and renamed vars. with more TRY-EXCEPT zones, more robust.
   -New function to encapsulate creation of OLE object ConnectToApp()
   -Create admits new flag to reuse the last created instance of excel.
   -NewDoc admits new flag to add or not a sheet to the new doc (related to the previous one).
   -RemoveSheet added in 3 flavours: by index, byname, and all except one name.
   -Added list of OLE constant for both Excel and OO so you can use them by name in your code.
   -Added FontColor, Underline and HorizontalAlignment properties to cells.
   Note: I added some properties so old vars names are still usable:
         Document, ActiveSheet and Programa.
 V1.02: Creating from a exiting file didn't set the AmericanFormat (thanxs Malte).
 V1.01:
   ***********************
   ** By Malte Tüllmann **
   ***********************
   -Excel2000/2003 save .xls files in a different way than 2007.
 V1.00:
   -Saving in Excel2007 will use Excel97 .xls file format instead of .xlsx
 V0.99:
   -Added a funtion by Alex Smith to set a cell text into italic.
 V0.98:
   -Added two procedures to easily send a number or a date to a cell position:
   SendDate(Row, Col, Date) and SendNumber(Row, Col, Float), if you look at
   the code you will notice that this is not so trivial as one could spect.
   -I have added (as comments) some useful code found on forums (copy-paste rows)
 V0.97:
   -Added CellFormula(col, row), similar to CellText, but allows to set a cell
   to a number wihout the efect of being considered by excel like a "text that
   looks like a number" (doesn't affect OpenOffice). Use it like this:
   CellFormula(1,1) := '=A2*23211.66';
   Note1: Excel will always spect numbers in this shape: no thousand separator
          and dot as decimal separator, regardless of your local configuration.
   Note2: Date is also bad interpreted in Excel, in this case you can use
          CellText but the date must be in american format: MM/DD/YYYY, if you
          use other format, it will try to interpret as an american date and
          only if it fails will use your local date format to "decode" it.
 V0.96:
   -Added PrintSheetsUntil(LastSheetName: string) -only works on excel- to print
   out all tabs from 1 until -excluded- the one with the given name in such a
   way that only one print job is created instead of one per tab (only way to do
   this in previous versions, so converting part of a excel to a single PDF
   using a printer like PDFCreator was not posible).
 V0.95:
   -ActivateSheetByIndex detect imposible index and allows to insert sheet 100 (it will create all necesary sheets)
   -SaveDocAs added a second optional parameter for OOo to use Excel97 format (rescued from V0.93 by Rômulo)
   -A little stronger ValidateSheetName() (filter away \ and " too).
 V0.94:
   -OpenOffice V2 compatible (small changes)
   -A lot of "try except" to avoid silly errors.
   -SaveDocAs(Name: string): boolean; (Added by Massimiliano Gozzi)
   -New function FileName2URL(Name) to convert from FileName to URL (OOo SaveDosAs)
   -New function ooCreateValue to hide all internals of OOo params creation
 V0.93:
   ***************************
   ** By Rômulo Silva Ramos **
   ***************************
   -FontSize(Row, Col, Size): change font size in that cell.
   -BackgroundColor(row, col: integer; color:TColor);
   -Add ValidateSheetName to validate sheet names when adding or renaming a sheet
   REVERTED FUNCTIONS (not neccesary in newer version V0.95 anymore)
   -Change AddNewSheet to add a new sheet in end at sheet list
   *REVERTED IN V0.95*
       It creates sheet following the active one, so to add at the end:
       ActivateSheetByIndex(CountSheets);
       AddNewSheet('Sheet '+IntToStr(CountSheets+1));
   -Change in SaveDoc to use SaveAs/StoreAsUrl
   *REVERTED V0.95*
       Use SaveDocAs(Name, true) for StoreAsUrl in Excel97 format.
 V0.92:
   -SetActiveSheetName didn't change the name to the right sheet on OpenOffice.
   -PrintPreview: New procedure to show up the print preview window.
   -Bold(Row, Col): Make bold the text in that cell.
   -ColumnWidth(col, width): To change a column width.
 V0.91:
   -NewDoc: New procedure for creating a blank doc (used in create)
   -Create from empty doc adds a blank document and take visibility as parameter.
   -New functions ooCreateValue and ooDispatch to clean up the code.
   -ActiveSheetName: Now is a read-write property, not a read-only function.
   -Visible: Now is a read-write property instead of a create param only.
 V0.90:
  -Create from empty doc now tries both programs (if OO fails try to use Excel).
  -CellTextByName: Didn't work on Excel docs.