Susanne,

Try this. It assumes you working day is 08:00 - 16:00 hrs so change to suit.
Format
the cell as [hh]:mm

Holidays is a named range that contains holiday dates. If you don't want
this simply delete ',holidays' form the formula

=(NETWORKDAYS(A1,B1,Holidays)-1)*("16:00"-"08:00")+MOD(B1,1)-MOD(A1,1)

Mike


"Susanne" wrote:

Can you please help me. I need to calculate the difference between two dates
which also contain the timestamp but I would like it to only count the normal
working time - 8 hours per day and not weekends