Try this then
Private Sub Form_Current()
If (Me.Tekst0 = "TBD") Then
Me.Kader2 = 2
Else
Me.Kader2 = 1
End If
End Sub
Where tekst0 is the name of the textbox, kader2 is the name of the option group.
2 is the value of TBD
1 is the value of NA, to change in code if different on your DB