How can I get a vb.net mobile app to respond to the PDA buttons?

The following code appears to work when deployed to emulation but not when deployed to the device:-

Code:
    Private Sub App_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles MyBase.KeyDown

        If (e.KeyCode = System.Windows.Forms.Keys.Up) Then
            'Rocker Up
            'Up
        End If
        If (e.KeyCode = System.Windows.Forms.Keys.Down) Then
            'Rocker Down
            'Down
          End If