How to let visio shapes change behaviour from their text?

I have shapes that should change behaviour on the basis of their text.

Text fields change their height and with using =GUARD(TEXTWIDTH(TheText)) just fine.

But when I try to let something change color like this =THEMEGUARD(IF(LEN(TheText)>3,RGB(255,112,192),RGB(0,112,192))) nothing happens when you change the text.

Any ideas on how to get visio to actually run this like it should? Or am I doing something wrong here?

Or am I doing something wrong here?

Please try add SHAPETEXT function.

With syntax like =THEMEGUARD(IF(LEN(SHAPETEXT(TheText))>3,RGB(255,112,192),RGB(0,112,192)))

I check this formula at my side, it works!