How do I disable the Print Screen Key?

I'm trying this:

Private Sub txtText_KeyDown(KeyCode As Integer, Shift As Integer)
If KeyCode = vbKeyPrint or KeyCode = vbKeySnapshot then
KeyCode = 0
End If
End Sub

But, when I press the Print Screen Key the event isn't fired. *ONLY* with Print Screen Key!!!

Thanks in advance,

Piazza