Piviot Table Setup

Hi,

I have a piviot table setup with the information below.

Count of Incidents, by year, by month, by system, by
problem type (request)

What I am trying to do is say what is the percentage of
requests vs incidents to be displayed a pie chart. So lets
say of the total of incidents 49% are requests and 51% are
incidents. Manually I would need to take the total of
incidents and subtract the requests...Can I do this with a
PV table???
Can someone please help me with this one? I think I am
missing something here....

Number Of Incidents
Year Month System Prob Type Total
2004 JUL GLOBAL TRADE SV REQUEST 140
GLOBAL TRADE SV Total 140
JUL Total 140
2004 Total 140
Grand Total 140