How can I change the value of a combo box based on value of an unbound text box?

You did not mention when you want the status combo box to change and how it should change so I shall assume you want to change it after you change the totaldue text box and if totaldue is zero, status should be Paid otherwise status should be Partial. If this is the case, in the totaldue textbox after update event place:

Private Sub totaldue_AfterUpdate ()
If totaldue then
   status = "Paid"
Else
   status = "Partial"
End if
End Sub

The after update event only fires if the user makes a change to the control.

Partial is where the text box (discount1) has a value >0, but total due still has a value >0. Example if the invoice is 1000.00 and they only make a payment of 700.00 leaving 300.00 due.

I put the code in the After Update event. The status does not change, when the total due is is > 0 or < 0. The totaldue is a unbound text box that calculates, could that be a problem?

Ok I place the code on a command button and it works, so it must be the event After Update. Any ideas?

As I stated, The after update event only fires if the user makes a change to the control. It unio not fire if it is a calculated control or if you change it in VBA. So the question is, when do you want the status combo box to show the new status? What event or events triggers that?

Is see. There is a sub form called invdetail. It should fire after I  make any changes to the sub form. How would I do that?

You can put the code in the sub form's after update event. That event will fire when changes are made to the sub form and the changes are saved to the underlying table by moving to a new record, closing the form, the pressing shift Enter (save record), clicking on save record or any other method that saves the record. If you want the status to change immediately after changing a control in the sub form, you would need to call the code from the after update event of each control.

I am having trouble refering to the main form. My subform is called invdetail and the main form is called frminvoicetable subform. The frminvoicetable subform is located on an unbound subform object called objSubform. I use this to help the form load quicker becuase it has 5 or 6 subforms. For some reason I have never been able to refer to subform loaded on the unbound subform object. I have included the code on the unbound object. The object is on a tab control and loads teh correct subform on the chage event of the tab control. All the subforms are part of the parent form frmsubjects.

Private Sub TabCtl300_Change()

   Dim strSubformName As String
   Select Case Me.TabCtl300
      Case 1: strSubformName = ""
      Case 2: strSubformName = "frmupdatetable subform"
      Case 3: strSubformName = "frmletters"
      Case 4: strSubformName = "frminvoicetable subform"
      Case 5: strSubformName = "frmlog"
      Case 6: strSubformName = "frmtimeline"
      Case 7: strSubformName = "frmprocess"
      Case 8: strSubformName = "frmadditionalsubject"
      Case Else: strSubformName = ""
   End Select
   If strSubformName = "" Then
      Me.Form.objSubform.visible = False
   Else
      Me.objSubform.SourceObject = strSubformName
      Me.objSubform.LinkMasterFields = "subjectid"
      Me.objSubform.LinkChildFields = "subjectid"
      Me.objSubform.visible = True
     
   End If
End Sub

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From a subform, you can refer to the "parent" form by doing this:

Me.parent.SomeControl

From the Parent, you can refer to your subform like this:

Me.objSubform.Form.SomeControl

I'm not clear which way you're going, so I cannot really comment further.

Thanks.