Bernhard,
Look at it this way
the last day of this week= the first day of next week minus one day.
So if you have a function for the FDOW (firstdayofweek)
then

? FDOW(date()) prints the first day of this week
? FDOW(date()) + 7 prints the first day of NEXT week
therefore
? FDOW(date()) + 6 prints the LAST day of this week.

Wouldn't you agree?

Peter