I've got an invoicing macro that totals 4 amount boxes and a amount
paid box (input boxes on the form). I'm trying to get the total box to
update based on the amounts in this box, but i keep getting a type
mismatch, here's what i have for the change events on the five inpute
boxes

Private Sub FirstAmtBox_Exit(ByVal Cancel As MSForms.ReturnBoolean)
BalanceDueAmountBox.Value = ((FirstAmtBox.Value * 1) +
(SecondAmtBox.Value * 1) + _
(ThirdAmtBox.Value * 1) + (FourthAmtBox.Value * 1) -
(AmtPaidBox.Value * 1))
End Sub

any suggestions?