Pivot Table - Percentage Of Data Of Type

I have a pivot table based on data in the form (simplified);

Year Cat 1 Sex
1 a F
1 A M
1 B U
1 B F
2 A M
2 A M
ETC. ETC. ETC.

So in the pivot table we have year 1 in the first row year 2 in the second etc. cat 1 as the column headings.

What i want to do is get the data item area of the pivot table to display the percentage male female etc by year, something like =(Count of F in Sex)/(Count of Sex), how can I do this?

So year 1 would be 50% Female, 25% Male, 25% Undefined.

Re: Pivot Table - Percentage Of Data Of Type

Thanks, I was being very silly. I will have a play, looks as though I am going to have to use several pivot tables to get what I want, which is Male/Female as a percentage of A or B in cat1 and both A&B.