Graphic, zoom function

Question

I am dealing with a zoom equation. Scope of work is to keep the mouse position as pivot when I zoom. I mean, if a select a point in the picture, the world should become bigger all around the mouse position, but the line, arc or what else exactly down the mouse, should remain in this position. My be, what for me took a lot of time, for those that make graphic each day, is a kid game. This is my actual zoom function. xo,yo are the coordinates of the point 0,0 of the shape.

 Private Sub dlgSelectShape_MouseWheel(ByVal sender As Object, _
     ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseWheel

    Dim p As Point
    p = e.Location
    p = Me.PointToScreen(p)
    p = PictureBox1.PointToClient(p)
    If p.X > 0 And p.Y > 0 Then
        If e.Delta > 0 Then
            'lscale =scale factor
            lscale = 0.01 * e.Delta * lscale

        Else
            'lscale =scale factor
            lscale = -lscale / (0.01 * e.Delta)


        End If
        'xo = point of origin it is the coordinate of the point (0,0)
        xo = xo + (-xo + p.X) * lscale / 2
        yo = yo + (yo - p.Y) * lscale / 2
        Draw()
    End If

  End Sub