public override void Calculate(GridCalculationData data) { // Calculate MYTESTFUNC() with your own logic. i.e Multiply MYTESTFUNC() parameter with 2 so MYTESTFUNC(3.0) = 6 if ("MYTESTFUNC".Equals(data.FunctionName.ToUpper())) { data.CalculatedValue = (decimal)(2.0 * (double)data.GetParamValue(0)); } }