I have a cell that has a validation table that allows data to be entered that
is not available in my "list". It brings up the information pop up window
and you click ok to keep going with the information entered that is not on
the list.

Another cell has a vlookup table dependent on the data in the validation
cell. I would like for the vlookup cell to return nothing if the validation
cell had data entered on it that is not included on the validation list. If
I put the last argument in the Vlookup, it returns an N/A #. My formula
looks like this:
=IF($E$120, VLOOKUP($E$12,$AB$3:$AC$34, 2, 0 ), "")

Any thoughts?

Thanks!