I'm trying to create a drop-down list (in Data Validation) that is populated
by the subset of a larger list. The larger list is not sorted, nor can it
be. If possible, I'd prefer not create a subset list elsewhere in the
worksheet and have a list in Data Validation refer to it. Ideally, I'd like
to enter a formula in the Source: box (after choosing List under Allow: in
Data Validation) that would create a filtered list from the larger list.

It's difficult for me to explain this well, but maybe an example will help:

I have a table of baseball players, 20 rows by 3 columns (columns are
Position, Name and Batting Avg.). I'd like to create a pull-down menu, below
the main menu, with just first basemen in it (and let's assume there are 3
first basemen in the larger list).

Any help is greatly appreciated, I've been struggling with this for a while.