business rule BR for a column (e.g. K) to Accumulate what is in another column (in Cubeview)?

As it turns out, I had to write a new BusinessRule.Finance.XFR_CV_BR_Accum_colum
Here's the heart of the code:

Dim cellVal As Decimal = api.Data.GetDataCell("U1#" & api.Pov.UD1.Name).CellAmount

' add accumulative value to current cell value
accumVal = accumVal + cellVal