The HostEventParam property retrieves or sets a value that indicates the current's event parameter. The HostEvent is fired each time the host fires a event. In other words, the HostEvent event forwards any event that the host may fire. Each event has different number of parameters, which is indicated by the HostEventParam(-1) property. Each parameter of the event can be accessed through the HostEventParam property. The HostEventParam(-2) gives a general information of the event. 

The following VB sample displays information about the host's events:

Private Sub G2Host1_HostEvent(ByVal EventID As EXG2HOSTLibCtl.HostEventEnum)
    Debug.Print G2Host1.HostEventParam(-2)
End Sub

The following VB sample displays a message box, before pressing the Delete key, and cancel the operation if user selects No or Cancel:

Private Sub G2Host1_HostEvent(ByVal EventID As EXG2HOSTLibCtl.HostEventEnum)
    If (EventID = exHostKeyDown) Then
        If (vbKeyDelete = CInt(G2Host1.HostEventParam(0))) Then
            If Not (MsgBox("Do you want to delete?", vbYesNoCancel) = vbYes) Then
                G2Host1.HostEventParam(0) = 0
            End If
        End If
    End If
End Sub

You can disable completely deletion by removing the exHostAllowDelete flag from the HostReadOnly property.