Well, if you're corrcet in saying that txtTranxAmt , is
calculated, then why are you trying to assign a value to it?
Me.txtTranxAmt = Me.txtActualAmt / Me.txtActProd??
Calculated means the contol source of the field,
has a predifened value.
Is that the case with Me.txtTranxAmt?
just because you make a calculation for it, via VBA,
doesn't mean it's calculated BUT,
the error message seems to imply you have an expression,
in the control source of Me.txtTranxAmt ?
either assign a value to it Via VBA or,
in the controlSource of the control put,
=Val([txtActualAmt] / [txtActProd])