Hi,
If you mean just Friday i.e. a single day as the weekend try this
=SUM(IF(ISERROR(MATCH(WEEKDAY(ROW(INDIRECT(A1&":"&B1))),{5},0)),1,0))
with your start date in a1 and end date in B1
This is an array formula which must be entered with CTRL+Shift+Enter and NOT
'just enter. If you do it correctly then Excel will put curly brackets around
'the formula{}. You can't type these yourself. If you Edit the ranges
'then you must re-enter as An array.
Mike