Tooltip control with MaskedTextBox in VB.Net

Hi,

I was reading and trying the maskedtext box sample given in VB.Net 2008 from MSDN. Following is the code:
 Private Sub maskedTextBox1_MaskInputRejected(ByVal sender As Object, ByVal e As System.Windows.Forms.MaskInputRejectedEventArgs) Handles maskedTextBox1.MaskInputRejected
        ToolTip1.ToolTipTitle = "Input Rejected"
        ToolTip1.Show("You can only add numeric characters (0-9) into this date field.", maskedTextBox1, 0, -20, 3000)
    End Sub

Here:
a. Why are the parameters  and -20 taken? It seems they are x and y co-ordiantes for the toltip ballon. But how are they arrived at?

b. What if I do not want to hard-code these values? Since they may change based on the screen resolution of the user?

c. If I remove these values, the tool-tip ballon goes anywhere. how can I ensure that the baloon is display at the start of the masked textbox?

Regards,
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