Ooooh. Tricky one, Adina!
In theory, I think you'd either need:
a valueexpression "on the label" as well, or
some kind of wrapper around the entire optional shared column that makes the entire cell visible or invisible (e.g. height = 0), or
some kind of substitution around the whole shared column that replaces "labels without values" with null, after the fact
So...I'm going to go with "can't be done" on this one. Hats off to anyone who proves me wrong, as always, of course. And if you still need a solution but do decide to give up, I'd be happy to discuss using our Magic Reports solution for it with you.
Regards,
Doug