I am trying to do a Vlookup between two different workbooks. When I enter "false" at the end, it gives me a n/a in the column I want my number to appear. I believe the problem is because they are not both Excel 2007 files - one may have been a CVS file originally and saved as Excel.xlsx and the reason I think this is because I copied & pasted one of the matching addresses from my master file onto the spreadsheet I am looking to pull a reference number from and once I did that, the vlookup worked correctly. The problem is, my master has 150 addresses and the reference workbook has over 700 - how do I convert the reference workbook to the same type of file (they are both saved with .xlsx extensions) and make my vlookup work correctly?