Crystal Report Running Totals

I am working in the Crystal Report Environment (IDE).

 

 

I am trying to create a running variable and substract from the total base upon an condition.

 

For example: If Total is greater than 80, take the total and subtract 80 from the total. If we apply that condition below. The difference will be 10.

 

90 is greater than  80. So there for 90-80 = 10

 

 

ColorId     ColorItem  ColorTotal

1                     red                30

2                     blue              20

3                     black             40

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                         Total =       90