'Or something else caused XL to decide...' At that point I'd try to tell
XL in words what it has to do ;)

thanks for that hint. with the functions I wrote, the performance is
still acceptable but not as good as it could be - i think.

Tushar Mehta wrote:
In article , says...
Does that mean, that if I pass a defined range, the function would only
be relaunched, when something in that range changes?

Essentially, yes. Unless some other argument changed. Or something
else caused XL to decide to recalculate your function anyway.