Polygon fill not working properly

Question

I am having a problem filling a polygon. When I use FillPolygon I get a fill that often overlaps the boundary polygon. How can I force the fill to stay within the boundary. I have some code to show what I've attempted. I hope this isn't the only way to do it!

Private Sub pbox2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles pbox2.Click

        Dim myGraphics As Graphics

        Dim myPoints() As Point

        Dim myFillPoints() As Point

        Form1_MouseClick(sender, e)

        Dim PtFill1 As Point = New Point(insPoint.X + 1, insPoint.Y + 1)

        Dim PtFill2 As Point = New Point(insPoint.X + 20, insPoint.Y + 1)

        Dim PtFill3 As Point = New Point(insPoint.X + 20, insPoint.Y + 21)

        Dim PtFill4 As Point = New Point(insPoint.X + 60, insPoint.Y + 21)

        Dim PtFill5 As Point = New Point(insPoint.X + 60, insPoint.Y + 40)

        Dim PtFill6 As Point = New Point(insPoint.X + 40, insPoint.Y + 40)

        Dim PtFill7 As Point = New Point(insPoint.X + 40, insPoint.Y + 60)

        Dim PtFill8 As Point = New Point(insPoint.X + 21, insPoint.Y + 60)

        Dim PtFill9 As Point = New Point(insPoint.X + 21, insPoint.Y + 40)

        Dim PtFill10 As Point = New Point(insPoint.X + 1, insPoint.Y + 40)

        Dim pt1 As Point = insPoint

        Dim pt2 As Point = New Point(insPoint.X + 20, insPoint.Y)

        Dim pt3 As Point = New Point(insPoint.X + 20, insPoint.Y + 20)

        Dim pt4 As Point = New Point(insPoint.X + 60, insPoint.Y + 20)

        Dim pt5 As Point = New Point(insPoint.X + 60, insPoint.Y + 40)

        Dim pt6 As Point = New Point(insPoint.X + 40, insPoint.Y + 40)

        Dim pt7 As Point = New Point(insPoint.X + 40, insPoint.Y + 60)

        Dim pt8 As Point = New Point(insPoint.X + 20, insPoint.Y + 60)

        Dim pt9 As Point = New Point(insPoint.X + 20, insPoint.Y + 40)

        Dim pt10 As Point = New Point(insPoint.X, insPoint.Y + 40)

        myGraphics = Graphics.FromHwnd(hwnd:=ActiveForm().Handle)

        ReDim myPoints(9)

        ReDim myFillPoints(9)

        myPoints(0) = pt1

        myPoints(1) = pt2

        myPoints(2) = pt3

        myPoints(3) = pt4

        myPoints(4) = pt5

        myPoints(5) = pt6

        myPoints(6) = pt7

        myPoints(7) = pt8

        myPoints(8) = pt9

        myPoints(9) = pt10

        myFillPoints(0) = PtFill1

        myFillPoints(1) = PtFill2

        myFillPoints(2) = PtFill3

        myFillPoints(3) = PtFill4

        myFillPoints(4) = PtFill5

        myFillPoints(5) = PtFill6

        myFillPoints(6) = PtFill7

        myFillPoints(7) = PtFill8

        myFillPoints(8) = PtFill9

        myFillPoints(9) = PtFill10

        For Each pts As Point In myPoints

            If pts.X < 50 Or pts.X > 170 Or pts.Y < 140 Or pts.Y > 340 Then

                MsgBox("Shape falls outside of range." & vbCrLf & "Select a different insertion point.", MsgBoxStyle.OkOnly, "WARNING")

                Exit Sub

            Else

                Continue For

            End If

        Next

        myGraphics.DrawPolygon(pen:=Pens.Black, points:=myPoints)

        myGraphics.FillPolygon(Brushes.Indigo, myFillPoints)

    End Sub