ขออนุญาติครับ ช่วยบอกวิธีลบเส้นใน Picturebox ครับ Vb.net 2013

Public Class Form1
    Public BMP As New Drawing.Bitmap(900, 500)
    Public GFX As Graphics = Graphics.FromImage(BMP)


 Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        GFX.Clear(Color.White)
        PictureBox1.Image = BMP
    End Sub


 Private Sub brem()
        ArrBremX(IndexPoint) = ((Arrayx(IndexPoint) * 20) + 20)
        Form1.GFX.DrawLine(Pens.Black, New Point(20, 200), New Point(ArrBremX(IndexPoint), 200))
        Form1.PictureBox1.Image = Form1.BMP
        Debug.Print("IndexPoint =" & IndexPoint)

    End Sub