|That's the problem! For some reason when setting the left box, the exclamation point was in there, but it was missing from the setting of the right box. That usually flags an warning on compile. I wonder why it wasn't.
It appears SetItemData is doing something though. The value returned with GetItemData is always the last value on the list. The list redraws after a move, so all the items were probably getting set to the last value for some reason I don't understand.
It works now.
I think I need glasses...