Hi All

Can anyone help me with a formula to calculate the Week Commencing date based on a date supplied?

I found this:
http://www.bygsoftware.com/Excel/fun.../iso_dates.htm

and tried:
=1+INT((A1-DATE(YEAR(A1+4-WEEKDAY(A1,2)),1,5)+WEEKDAY(DATE(YEAR(A1+4-WEEKDAY(A1,2)),1,4),2))/7)

Using a date in A1 of "28-Sept-05" (formatted) but this returns a completely wrong date "08/02/1900"

Am I doing something wrong?

Excel Version 2000

Any help appreciated. Thanks
Jules