Hi Jeffrey
Apologies for not making my "challenge" clearer in the first place.
The number of working days between the 1st and 22nd June is 16 (excluding weekends).
many thanks for your help to date.
Tony

ps: I just stumbled across the www.cpearson.com website which gives me a solution for a single row as follows:
=MAX(0,NETWORKDAYS(MAX(C$1,Sheet1!$E5),MIN(DATE(YE AR(C$1),MONTH(C$1)+1,0),Sheet1!$F5)))
This works exactly as I need it but my challenge is how to wrap this in a SUMPRODUCT function so I get a total for all skillsets.
Any help appreciated Jeffrey.
Thanks
Tony