Public Class Form1
    Dim plist As New List(Of Point)
 
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        plist.Add(e.Location)
        PictureBox1.Invalidate()
    End Sub
 
    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        For Each pt As Point In plist
            e.Graphics.DrawLine(Pens.Black, pt.X - 5, pt.Y, pt.X + 5, pt.Y)
            e.Graphics.DrawLine(Pens.Black, pt.X, pt.Y - 5, pt.X, pt.Y + 5)
        Next
    End Sub
End Class