I've tried a variety of ways to accomplish the following:

I have one column (C) with various categories and a second column (D) that
has dates associated with some and others are blank.

B C D
NAME ROLE INTERVIEW
bill reception 14-mar-01
john driver
harry driver 1-apr-01
frank installer 6-jun-01
mary driver
ann reception 4-oct-01

I want to sum the number of interviews I have conducted for each category of
role. Ideas?