Excel 2007 : VLOOKUP Question

Hello,

I am trying to do a VLOOKUP function on a listing of request ID numbers against another list of request ID numbers to see if there are any missing from the 2nd list. The fist list contains 94 request ID's, while the 2nd list contains 90 request ID's. The 2nd list is essentially the conpleted requests, while the first list all havent nessasarily been completed. I have set the data up so the complete requests are in column A, the original list are in column B, how should the VLOOKUP formula look like?