I'm not sure what you mean about "keep the 4000 names", but to get the thousand that match try this:
In cell C1 enter this formula:
=IF(ISNA(VLOOKUP(A1,$B$1:$B$100,1,FALSE)),"",VLOOKUP(A1,$B$1:$B$100,1,FALSE))
then go to cell a1 and do the following:
hit End, then DownArrow
RightArrow 2 times (now in col C at the bottom of the list of names in col A)
Hold Shift then hit End, then UpArrow
now hit Alt + E, then I, then D.
now just hide column B and you should have a column of names next to Col A where the names match, and nothing showing next to names where there is no match...
That what you wree looking for?
Cory
Wait! I just figured out what you really want after reading your post more closely. I'll have to work on it a minute (unless someone else answers first)...
Cory
Cory is correct, but seems to be keeping the matches rather than the non matches. Assuming the 1000 names in B all appear in A, I think the formula would work as:
=IF(ISNA(VLOOKUP(A1,$B$1:$B$1000,1,FALSE)),A1,"")