I have a problem working with this function:

NETWORKDAYS(start_date,end_date,holidays)

This function calculates the number of "Working Dates" between any two given
dates. My problem is that this function calculates Saturday and Sunday as
none-working days, but in the country Im working in, we have Friday and
Saturday as our none-working days. Therefore, it gives an inconsistent
answer. Do you have any idea if can I make the function start calculating
Friday and Saturday as the official none-working days?!