Sorry for re-opening this thread, but ...

... to work with negative values the {REF Text1} = {=Text1} part has to be formatted the same way, the FormField is formatted: e.g. {REF Text1} = {=Text1 \# "0,00"}. Otherwise IF will return FALSE.

That's at least what I experienced. Now each value is accepted and calculated the way it should be.

Cheers
NP