I do not have a Group Selection formula. I've never used it, I have always depended on the Group Expert, which has worked well so far. Currently, in the Group Expert, I have the formula I referred to in the OP.
So, let's say that I need to start using the Group Selection formula. What do I do with the Group Expert? Leave it like it is, or remove the current selection? If I remove the current selection, what will that do to the form (specifically the Group Header #1 and Group Footer #1)?