Use a richtextbox.
[highlight="VB.Net"]Dim Image As New System.Drawing.Image
If My.Computer.Clipboard.ContainsImage() Then
ClipImage = My.Computer.Clipboard.GetImage
End If
'You may assign an image from the resources to your clipboard aswell.
If Image IsNot Nothing Then
RichTextBox1.Paste()
End If
[/highlight]
You now just have to assign the image from the resources to the clipboard.
Now you need to find the textposition of the text you want to change, replace the text, paste.