Put this formula in I9.

=VLOOKUP($H9,THREED('[Purchase Invoice Board June 08 - May 09.xls]Mar 09:Jan 09'!$A$4:$J$400),3,0)

It should pull up the CompanyInvoice number

I changed the Columns() part to hard coded 3 because it seems you are pulling from different columns and not necessarily consecutive columns...

so you would have to paste the same formula in the other cells and change just the 3 to the appropriate column number you want to extract from.

Make sure that the reference file has still the same name and that the sheet names are the same... i.e. you may have to change this part around '[Purchase Invoice Board June 08 - May 09.xls]Mar 09:Jan 09' to suit your actual workbook identity.

This part: $A$4:$J$400 references the whole table on each sheet so you may also need to adjust to ensure all data is being looked at.