Okay... I think I have figured out my own question... I use the
following formula and it works just fine:

=IF(AND(F6="",E6<D6),NETWORKDAYS(E6,D6,M$6:M$14)-1,IF(AND(F6="",E6D6),NETWORKDAYS(E6,D6,M$6:M$14)+ 1,IF(AND(F6="",E6=D6),"0",IF(F6<"",NETWORKDAYS(F6 ,D6,M$6:M$14)+1,0))))

However, if anyone has something a little more direct or simple, I am
always open to learning new approaches! Thanks for your time...