I assumed it could be range driven, but in the example above, I don't ever come close to falling outside this range?
I think like Jack hinted, it is the amount/size of numbers after the decimal place (i'm sure there is a better term for that.. precision?).
CellAmount accepts a decimal so falls over when you try to send the value there.
I wonder if you could (if its acceptable) store the value in a double and then round it and send it to CellAmount?
So
Dim DoubleCellAmount = CAGRCalc.Cellamount ^ ExponCAGR - 1
CAGRCalc.CellAmount = Math.Round(DoubleCellAmount,X)
where X is some value that is acceptable to you
