=SUM(N(FREQUENCY(IF(C1:C20="Yes",MATCH(A1:A20&B1:B20&C1:C20,A1:A20&B1:B20&C1:C20,0)),MATCH(A1:A20&B1:B20,A1:A20&B1:B20,0))>0))
This is an array function, so it must be entered using Ctrl+Shift+Enter (not
just enter). Hope that works for you..
Alternatively, try this
=SUM(N(FREQUENCY(IF(C1:C20="Yes",MATCH(A1:A20&B1:B20&C1:C20,A1:A20&B1:B20&C1:C20,0)),MATCH(A1:A20&B1:B20&C1:C20,A1:A20&B1:B20&C1:C20,0))>0))
Regards,
Ryan---

Signature
RyGuy
> The function that I have tried to use, but does NOT work is:
>
[quoted text clipped - 6 lines]
> >
> > Is there a way to perform this function that I am trying to do??