Ora ho trovato forse come gestire meglio l'evento:

codice:
Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs)_ 
Handles WebBrowser1.DocumentCompleted
AddHandler WebBrowser1.Document.Body.KeyDown, New HtmlElementEventHandler(AddressOf WebBrowser1_KeyDown)
End Sub 

Private Sub WebBrowser1_KeyDown(ByVal sender As Object, ByVal e As HtmlElementEventArgs)    
If e.CtrlKeyPressed And e.KeyPressedCode <> Keys.ControlKey Then        'CTRL+SomeKey was pressed
	'handle it whatever way you want to
	MsgBox("CTRL + " & Chr(e.KeyPressedCode))
End If

End Sub
Questo intercetta la pressione del tasto. Rimane ora come disabilitare la tastiera...