'Use XMLDOM
set xmlDoc = createobject("Microsoft.XMLDOM")
 
'Open Source File for editing
xmlDoc.Async = "False"
xmlDoc.Load("C:\test.BLAS_VPAI")
 
set RACKS = xmlDoc.selectSingleNode("/TEST_PLAN/RACKS")
for i = 1 to NumOfDPplates
   set NewRackNode = xmlDoc.createElement("RACK")
   NewRackNode.setAttribute "barcode", "DPbarcode"&i
   NewRackNode.setAttribute "action", "ins"
   RACKS.appendChild(NewRackNode)
   set NewRackNode = Nothing
next
 
'Save xml and exit xmlDoc
xmlDoc.Save("C:\test_new.BLAS_VPAI")

<RACKS><RACK barcode="DPbarcode1" action="ins"/><RACK _
  barcode="DPbarcode2" action="ins"/><RACK barcode="DPbarcode3" _
  action="ins"/><RACK barcode="DPbarcode4" action="ins"/><RACK _
  barcode="DPbarcode5" action="ins"/><RACK barcode="DPbarcode6" _
  action="ins"/></RACKS>

<RACKS>
<RACK barcode="DPbarcode1" action="ins"></RACK>
<RACK barcode="DPbarcode2" action="ins">></RACK>
<RACK barcode="DPbarcode3" action="ins">></RACK>
<RACK barcode="DPbarcode4" action="ins">></RACK>
<RACK barcode="DPbarcode5" action="ins">></RACK>
<RACK barcode="DPbarcode6" action="ins">></RACK>
</RACKS>