I am trying to get an average of time spent each month on an activity. The
spreadsheet has 12 months and only 3 of the months are populated.I think it
is still counting months 4-12 in my average. As each months time is entered I
want it to recalculate the average.

Example : April 120 min, May - 135 min, June 105 min
(Time is in minutes)

=IF(SUM($M$88,$P$88,$S$88,$V$88,$Y$88,$AB$88,$AE$8 8,$AH$88,$AK$88,$AN$88,$AQ$88,$AT$88)<=0,"",AVERAG E($M$88,$P$88,$S$88,$V$88,$Y$88,$AB$88,$AE$88,$AH$ 88,$AK$88,$AN$88,$AQ$88:$AT$88))

The above gives me the average of 30 min rather than 120 min. Please advise