Thank you both for your help.

I've had to ammend the forumla slightly as I had to strip down both the spreadsheets in order to upload them (too big!).

This is the formula I now have:

=IF(ISNA(VLOOKUP(F6,[Picklist1.xls]Pick!$D$2:$H$493,1,FALSE))=TRUE,0,VLOOKUP(F6,[Picklist1.xls]Pick!$D$2:$H$493,4,FALSE))

Thanks again