Get LOOKUP() Function To Only Look Up Exact Values

I've been using the LOOKUP() function and like it a lot only it has one feature I don't want. This one:

If the Lookup function can not find an exact match, it chooses the largest value in the lookup_range that is less than or equal to the value.

As I am working with text string instead of numbers this has resulted in a number of incorrect values being returned. I would like it if it could not find an exact match it would just return an error or say "0", and not try to find a close match. Anyone know a fix for this?