Need Excel to look at weekdays in a formula

[ExcelBeginner85]

Hi I have a formula in my worksheet that looks at a date of expected completion (cell c3) and date of actual completion (cell e3) and tells me how many days over or under it is (cell g3)
but I need it to only take into account weekdays I am using the formula =IF(E3="","",C3-E3) could someone please tell me how this is done, Thank you in advance

[ragulduy]

=IF(E3="","",NETWORKDAYS(E3,C3))

I think.