Facing Issues With Draw Image Method

[Shohag_ifas]

Greetings...
hope all are fine..
i am trying to making a image effect.
Let say:
there is 3 picture box
when i click on a button picture1 drawn on picture3
now to do the effect again i set pic3=pic2
and click the button again. it's drawn the pic on on pic3
but the issue is it also change pic2 to pic1 (or may be to pic3) why

so, please download the attached file and help me out. I am stuck..

i had experience that many one don't want to download attachment for them: (but better if you download the vb.net source files)
Steps:
1. Create a new vb.net project (winform)
2. Place 3 Picturebox (size Mode Property to stretch image)
3. Now Add 3 Different Picture On The Picture boxes
3. Add A Button

Now Use Bellow Source Code:

Public Class Form1
    Dim bmp1 As Bitmap
    Dim bmp2 As Bitmap
    Dim grpDst As Graphics
    Dim FromRect As Rectangle
    Dim ToRect As Rectangle

    Private Sub cmd1_Click(sender As System.Object, e As System.EventArgs) Handles cmd1.Click
        bmp1 = New Bitmap(PictureBox1.Image)
        bmp2 = New Bitmap(PictureBox2.Image)
        grpDst = Graphics.FromImage(PictureBox3.Image)
        SDrawTest()
        PictureBox3.Image = PictureBox2.Image REM to load another image on pic3 to set pic 1 again
        PictureBox2.Refresh()
        PictureBox3.Refresh()
    End Sub

    Sub SDrawTest()
        FromRect = New Rectangle(0, 0, bmp1.Width, bmp1.Height)
        ToRect = New Rectangle(0, 0, bmp1.Width, bmp1.Height)
        grpDst.DrawImage(bmp1, ToRect, FromRect, GraphicsUnit.Pixel)
        PictureBox3.Refresh()
        System.Threading.Thread.Sleep(1000) REM to show what the effect does
    End Sub

End Class

Now just run and press the button 2 time (better if you gap few sec)

on 2nd run picture 2 changes to picture 1 (or may be 3) i don't know

but why?

i just want to show/draw the source image on target image

(May main gold is manipulating vb6 PaintPicture method)

any help would be highly appreciated

best regards