CR 10.2 - Error in formula???

I have a formula in which I'm getting the following error

"A field is required here"

on the highlighted code.

Code:

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Dim dblDifference as Double

dblDifference = CDbl({@Difference})

formula = Sum(dblDifference)

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Anyone have an idea what's causing this?

thanks,

Think about it.

If @Difference were = 1
dblDifference would = 1
Sum(dblDifference) would also = 1, so what is the point.

If you are just trying to Sum the @Difference formula.

Formula = Sum(CDBL({@Difference}))

The above still may cause an error depending on the actual @Difference formula.

I already tried your suggestion Bruce and it gave me the same error msg. But here is the formula for @Difference:

Code:

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Sum ({tblReport.invoicedAmt}, {tblReport.custNO}) - Sum ({tblReport.advProdTotCost}, {tblReport.custNO})

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Both tblReport.invoicedAmt and tblReport.advProdTotCost are defined as Integers.