Having problems with the "Null"

Hello,



I have a code that when I delete my entry on the form it gives me



Run-time error '94: Invalid use of Null



Here is my code



Private Sub Remarks1_AfterUpdate()

Dim rst As DAO.Recordset

Dim strRemarks As String



strRemarks = Me.Remarks1

If strRemarks = "" Then Exit Sub



Set rst = CurrentDb.OpenRecordset("Final_Table")

'strRemarks = Me.Remarks1

Do

rst.Edit

If Nz(rst![BC1Chng1]) <> "" Then

rst![Remarks1] = strRemarks

Else

rst![Remarks1] = Null

End If

rst.Update

rst.MoveNext

Loop Until rst.EOF



End Sub

Having problems with the "Null"