VBA If/Then statement for autofill in Access Form

I am using VBA code to autofill an access form. So if you select 1, the next question should autofill to 9.

Private Sub PAC9_2b_FullyAdherent_AfterUpdate()
If [PAC9_2b_FullyAdherent] = 1 Then 
[PAC9_2a_IfNoAdherence] = 9
End If
End Sub

I cannot determine if there is something wrong with the codes or the individual fields. Many of my other statements are working, just not ones under this particular Sub.