How to get size of object in clipboard

[AlistairG]

Hi I have a multi-item store of objects eg something like Glippy/Linux. Whats not needed is duplicate items coming from the clipboard eg text compare is easy, but with images not so easy; first image goes to clipboard, say a new image goes to clipboard I need to determine that its a new image, but there is no sizeof function for clipboard. EG if the image size is different, then its a new image. No good comparing all the time to a timage, as this would take excessive time. I did try stream.size but unless my code was wrong, no good either.
In other words I am checking the clipboard all the time in a timer loop. If text changes, thats saved somewhere, if picture changes then that should be saved somewhere.
Any advice?