I've stacked these to show each of them, layer these ontop of each other.
Now when the user selects the ComboBox Refresh it so the Query updates.
VBA
Private Sub cboGrade_GotFocus()
Me.Refresh
End Sub
When a Grade has been chosen from the ComboBox set the Grade TextBox to the value of the ComboBox, then Save the Record and then set the Focus of the other TextBox so that it comes to the forefront.
Private Sub cboGrade_AfterUpdate()
Grade = cboGrade '.Column(1)
Me.Dirty = False 'DoCmd.RunCommand acCmdSaveRecord
txtGrade.SetFocus
End Sub
This will now use the DLOOKUP to get value and display it. It will appear as if the combo is showing it but it isn't.