Pivot table - calculating on pivot fields

Hi all!

I've been looking on here but not found anything yet

When using a pivot table, I'm using COUNT to determine the number of instances values in a column of data (without caring what the raw data is).

This is fine, but I'm struggling to then perform simple calculations on the COUNT values in the pivot table as the pivot fields are the source, not the COUNT representations that are in the pivot table.

For example, I want to calculate one series of COUNTS as a % of another. I'm struggling to do this in the pivot table. Even doing this outside the pivot table, I need to manually enter the formula for each time (which doesn't scale in my rather large use case).

Attached is a simplified example. Any pointers would be hugely appreciated!

Thanks for the response JeteMc!

I'd not heard of Power Pivot before - looks like it does exactly what I need.
Shame it's not available for Office for Mac though - thank you MS