I have a data-validation list box. Is it possible for the source cells for
the list to be on another sheet from the one in which the list-box appears?

I know similar questions have been asked before (I poked around before I
submitted this), and one fellow suggested that a data-validation iist-box can
reference another sheet if the list on the other sheet is named. Sadly, I
don't know how to do this. If cell A1 on Sheet 1, for example, has a list box
whose source cells are Sheet 2, A1:A20, how do I assign a name to get the
validation to work? No matter what I do, I get a pop-up saying that
validation cannot reference other sheets. Help!