hi Artur,

eg for counting unduplicated number of clients of "CM"
it is an array formula to insert with CTRL+Shift+Enter
=COUNT(IF((B1:B100="CM")*(A1:A1000)*(ROW(A1:A100) ),1/FREQUENCY(MATCH(A1:A100&B1:B100,A1:A100&B1:B100,0) ,ROW(INDIRECT("1:"&ROWS(A1:A100))))))

isabelle

Le 2015-10-12 19:41, rtour957 a écrit :
Each clients has a unique number. Throughout a year they participate in
different activities coded e.g. IS, CM, SW. They may participate in only
one or all three of the activities.
I need to come up with the annual report that would track unduplicated
number of clients served in each of these activities.
Any suggestions on how to do this would be highly appreciated.

Thank you, Artur