Then you mess around until you get it right.
Private Sub txt_KeyUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles txt.KeyUp
If e.KeyCode = Keys.F1 Then
Dim x, y As Integer
Dim r As Rectangle = txt.RectangleToScreen(txt.Bounds)
x = (r.Left - txt.Left) + txt.Width
y = (r.Bottom - txt.Top) - txt.Height
Help.ShowPopup(Me.txt, "Help is at hand", New Point(x, y))
End If
End Sub