I have read the posts on passing a control to a function.  As long as my
control has some data in it, the function works fine.  If my control is null
I get a message "You tried to assign a null value to a variable that is not a
variant data type".

I have tried to set the value of the text control to "" before passing it,
but I still get the error.  Any suggestions?

Here is the code:

Private Sub txtAddr1_BeforeUpdate(Cancel As Integer)
 If Nz(Me.txtAddr1, "") = "" Then
   Me.txtAddr1 = ""
 End If
 Cancel = Check_Length(Me.txtAddr1, mlngAddr1_Lngth, True)

End Sub

Function Check_Length(txtCtrl As TextBox, lngLngth As Long, _
                     bln0Lngth_allowed As Boolean) As Boolean
'*****************************************************************************
'* Function: Check_Length
*
'* Purpose: Displays a message if the field length is too long or 0.
*
'*        Returns true if error found.
*
'*****************************************************************************
 Check_Length = False
 If Len(Nz(txtCtrl.Text, "")) > lngLngth Then
   MsgBox "Only " & lngLngth & " characters are allowed." & vbCrLf _
         & "Remove " & (Len(txtCtrl.Text) - lngLngth) & " characters." _
         , vbExclamation + vbApplicationModal _
         , "Too Many Characters"
         
   Check_Length = True
   txtCtrl.BackColor = vbRed
 ElseIf Len(Nz(txtCtrl.Text, "")) = 0 And bln0Lngth_allowed = False Then
   MsgBox "Field cannot be blank." & vbCrLf _
         , vbExclamation + vbApplicationModal _
         , "Blank Field Invalid"
         
   Check_Length = True
   txtCtrl.BackColor = vbRed
 Else
   txtCtrl.BackColor = vbWhite
 End If

End Function