Pivot view, changing autocalc

[Adam]

Thank you for trying to help

I have created a query and am using pivot table view. I want to see my membership counts by Male and Female, catagorized by month. I am good at using Excel Pivot tables and have set it all up except that the Sum autocalc function is greyed out and my only choice is Count (which does not give me totals). What do I need to do to enable the Sum function

Thank you

Adam