VLOOKUP Audit? Searched, but still need help...

So, I have two sheets (actually two files, new and old). In both sheets there is a unique client number in column A. I need to compare the two sheets to see which client numbers do not exist in the older sheet (looking for new client #'s) and output the results in another column.

Sounds simple, but the VLOOKUP function is not working and gives me the good-old "#NUM".

I have searched and searched and cannot find out why I cannot make the simple task work.

Thanks!

Try something like this, and let me know if it works: