label in group header does not dissapear using "print when" expression

Label in group header does not dissapear using "print when" expression.

I have a column with long values. I set for the column label in the group header, the textField in the Detail and the textField in the footer the same "print when" expression:

When the sum of that coulumn in the group is zero, do not print theese fields.

My guess is that the sum is calculated after the header is printed.

Greetings :D