Pivot Table, Divide by count of months?

LoL this is my worst Excel week EVER.

1. I have a pivot table that sums up the percentage of time spent in different activities (1-19) by month.

2. any activity reported must total 100 for that month. The spreadsheet then adds up the monthly totals and divides it by 12 giving you 1200 / 12 = 100%. (i didn't create this spreadsheet, i'm just trying to work around it to pull a report).

I can't get my pivot to divide the grand total by the amount of months the person entered activities for... In the document, (i changed the names) Dave matthews was here Oct, Nov & Dec., i need that 300 (OR 3.00) to be divided by 3 not 12 to get 100%.. None of my pivot formulas worked. and i can't divide by "count" of month because some people have a count of 16+ (worked on more than one project that month). THe pivot pulls off the repor2 worksheet.

any ideas? Document is attached. 2007

is there a way to divide by columns in a pivot? i.e. can i change the number format on the grand total to display as whole numbers only, and create a column to add activities 1-O19/Grand total? I tried something similar but it was a no go.