How to Undo DragDrop on DragLeave event

Hi,

I have a row of PictureBoxes side by side on my form.  I am able to drag and drop images between the boxes and display a message when entering and leaving each box.  I would like to be able to start at one box, hold the shift button and move my move over consecutive boxes that I want to copy to and then copy to all of them when I dragdrop at the last box.  Ideally I wanted the boxes I pass over to change colour or display the copy of the image in the first PictureBox.  I decided to use the DragEnter and DragLeave.. copying the image on the DragEnter as the mouse passed over it.  This does work, however if a user started dragging from PictureBox1 and passed over PictureBox2-4 (whilst still holding the shift button) then decided that only PictureBox1-3 should be the same.  They would expect to be able to go back to PictureBox3 and the image from PictureBox4 to return to the previous value.  Can anyone suggest a way to return to the original value in a Picturebox on the DragLeave event, or suggest a better way to acomplish this?  This is my first day using VB.net (only used Access VBA until now), I have also never worked with drag and drop before.....I hope this makes sence it is horrible to explain!  

DragEnter:
        If e.Data.GetDataPresent(DataFormats.Bitmap) Then
            If e.KeyState = 5 Then ' (1 for the mouse and 4 for the shift button)
                Label3.Text = "Drag plus shift"
                e.Effect = DragDropEffects.Copy
                PictureBox4.Image = e.Data.GetData(DataFormats.Bitmap)
            Else
                Label3.Text = "Drag"
                e.Effect = DragDropEffects.Move
            End If
        Else
            e.Effect = DragDropEffects.None
        End If

  DragLeave:
        Label3.Text = "Drag leave"
        Me.PictureBox4.Refresh()