Per Tom Ogilvy:
Also, perhaps you need to at
least temporarily populate the cell references to insure the formula does not
evaluate to an error.

That's the route I took. Created a bogus entry at the end of
each lookup table, populated with just a single underscore -
which is legal for a range name.

After .Adding the .Validation, I went back and removed the
underscores. Prolly ought to delete the range named "_" and
adjust the dimensions of the ranges to ignore the dummy rows...
but for now, I'm just gonna move on to the vLookup part...
--
PeteCresswell