IMO I would deconstruct the process to see where it breaks down .
Your final formula might be calculating "correctly" but the formuals inside it are not.
If this is a row level calucaltion plce both the {@Pmt} and {@ExtendedCost} field into the row and then do the math yourself to see you also get the zero results.
If this is group or report level data place theose fields in that location and do the same thing.
This should help you spot where the 'error' is.
Edited by DBlank - 16 Nov 2011 at 7:49am