Visual Basic GDI+ Drawing Lines - vb.net

Question

I am working on a simple VB interface that should allow the user to draw a line from the point the mouse is clicked down to whereever the mouse position is, then leave the line where the mouse button is released. I am new to VB GDI+ and could use some pointers or tips. I need it so that I can draw multiple lines on the same control panel and everytime I start a new line somehow make it that the Paint paint function does not have to loop through each line I already drew. Here is my Code:
Public Class Form1
Dim down = False
Dim ptA As Point
Dim ptB As Point
Dim ptC As Point
Dim ptStart As New List(Of Point) ' Starting point of each line
Dim ptEnd As New List(Of Point) ' Ending Point of Each line
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.DoubleBuffered = True
End Sub
Private Sub Win_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Win.MouseDown
down = True
ptA = New Point(e.X, e.Y)
End Sub
Private Sub Win_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Win.MouseMove
If down = True Then
ptB = New Point(e.X, e.Y)
Win.Invalidate()
End If
End Sub
Private Sub Win_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Win.MouseUp
down = False
ptC = New Point(e.X, e.Y)
ptStart.Add(ptA)
ptEnd.Add(ptC)
End Sub
Private Sub Win_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Win.Paint
e.Graphics.Clear(Color.Black)
e.Graphics.DrawLine(Pens.LawnGreen, ptA, ptB)
For i = 0 To ptStart.Count - 1
Win.CreateGraphics.DrawLine(Pens.LawnGreen, ptStart(i), ptEnd(i))
Next
End Sub
End Class
In order to keep my existing lines, I stored the points in a list and each time I move the mouse while drawing, I call the Paint function and each time it is called, it loops through each point and draws a line between them. Any suggestions would be greatly appreciated.
Thank you,
JD
** Edit
Public Class Form1
Dim down = False
Dim ptA As Point
Dim ptB As Point
Dim ptC As Point
Dim ptStart As New List(Of Point)
Dim ptEnd As New List(Of Point)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Me.DoubleBuffered = True
End Sub
Private Sub Win_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Win.MouseDown
down = True
ptA = New Point(e.X, e.Y)
End Sub
Private Sub Win_MouseMove(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Win.MouseMove
If down = True Then
ptB = New Point(e.X, e.Y)
Win.Invalidate()
End If
End Sub
Private Sub Win_MouseUp(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Win.MouseUp
down = False
ptC = New Point(e.X, e.Y)
ptStart.Add(ptA)
ptEnd.Add(ptC)
End Sub
Private Sub Win_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Win.Paint
e.Graphics.Clear(Color.Black)
e.Graphics.DrawLine(Pens.LawnGreen, ptA, ptB)
For i = 0 To ptStart.Count - 1
e.Graphics.DrawLine(Pens.LawnGreen, ptStart(i), ptEnd(i))
Next
End Sub
End Class