Dim s2 As System.Drawing.Graphics
    Dim s2 As System.Drawing.Graphics
    Dim x_1, y_1, x_2, y_2 As Integer
    'Dim x_1, x_2, x_3, y_1, y_2, y_3, z_1, z_2, z_3, zmax, zmin As Double
    Dim p1 As Pens
    Dim s As String
    Dim cc As Color
    Dim PenColor1 As New System.Drawing.Pen(System.Drawing.Color.Red, 5)
    Dim PenColor2 As New System.Drawing.Pen(System.Drawing.Color.Black, 1)

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        s2 = Me.CreateGraphics
        s2.DrawLine(PenColor2, 0, 0, 100, 100)
....

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click