Days of the week (to exclude Saturdays/Sundays)

I am trying to set up a spread sheet where dates are automatically calculated from the previous date using the formula Cell address + 1 (e.g. =Sum(a1+1) but I want to restrict it to the working week. The formula should say something like "=SUM (A1+1 if A1= Monday, Tuesday, Wednesday or Thursday but if A1 = Friday then A1 +3)"

I probably haven't explained that very well, but if anyone can help I would be grateful

Here, try his:

=A1+IF(WEEKDAY(A1,2)<5,1,3)

Fantastic - that works brilliantly - many thanks