Anil;
So, the answer to my question is...? I guess it is: that is impossible in this case to do it by software polling.

Ok, could make some more time (a lot) if I use flip-flop, I think that gives me full cycle to cycle period for polling the change of the signal, but I have to make some calculations if it is enough, after all, that program is going to do many other things as well... :-)

Was I stupid or what, thank you Anil.

Kari