app_design_frontend_default_default_layout_organicinternet_postcodeanywhere.xml

<layout version="0.1.0">
 <checkout_onepage_index>
  <reference name="head">
   <action method="addJs"><script>postcodeanywhere.js</script></action>
  </reference>
 </checkout_onepage_index>
 
 <checkout_multishipping_address_newshipping>
     <reference name="head">
      <action method="addJs"><script>postcodeanywhere.js</script></action>
     </reference>     
 </checkout_multishipping_address_newshipping>

 <checkout_multishipping_address_editshipping>
     <reference name="head">
      <action method="addJs"><script>postcodeanywhere.js</script></action>
     </reference>     
 </checkout_multishipping_address_editshipping>

 <customer_address_form>
     <reference name="head">
      <action method="addJs"><script>postcodeanywhere.js</script></action>
     </reference>     
 </customer_address_form>

</layout>