MajP, Thank you once again for your interest- I did think of trying out your other code for XIRR, and did get a result out of it.
I had to modify the line: "AccessXIRR = MyXIRR(Payments, Dates, GuessRate)" to "AccessXIRR = Format(Round(MyXIRR(Payments, Dates, GuessRate), 4), "Percent")" to get...