Can anyone tell me if it is possible to nested countif's. I.e. Basically the following function

=COUNTIF(O:O,NAME_OF_PERSON),COUNTIF(P:P,CALL_TYPE)

Basically I work in a sales office and the sales staff can either make a prospect call, a customer call or a supplier call. I need to be able to see how many Prospect calls John Smith has made, customer calls etc..........

Any help please would be greatly appreciated

Wayne