Crystal Reports Average Summary of formula field with Sum?

Message

   Hello,

I know there should be a way to do this, I just don't know how. I need to produce an average summary of {@TrimPercent}, which is placed in the details part of my report, but Crystal Reports doesn't give me that option because there is a SUM in part of the formula:

{@TrimPercent} = Totext(({@Trim} * 100 ) / {@PaperWidth}) + '%' 

where
{@Trim} =
(({report_CorrugatorProductionView.PaperWidth}) /1000000) - Sum ({@OrderWidth}, {report_CorrugatorProductionView.SetupId})

{@PaperWidth} = {report_CorrugatorProductionView.PaperWidth}/ (1000000) 

{@OrderWidth} = {report_CorrugatorProductionView.Outs} * {report_CorrugatorProductionView.Width} / 1000000

How can I insert a summary for @TrimPercent? I have been trying to take out SUM of the formula and do a Running Total of that part but didn't work. I would appreciate any suggestions or thoughts about this. Thanks in advance.

-RZ 