Чем не угодило обработка события формы "Текущая запись"?
Private Sub Form_Current()
On Error GoTo Err_Form_Current
With Me
.Поле.Locked = False
'.Поле.Enabled = True
If .Поле.Value > 0 Then
.Поле.Locked = True
'.Поле.Enabled = False
End If
End With
Exit_Form_Current:
Exit Sub
Err_Form_Current:
MsgBox Err.Description & vbCrLf & Err.Number, vbCritical, Form [MyForm] -> Sub [Form_Current]"
Resume Exit_Form_Current
End Sub