Refresh UI display during event processing

Hi All

I have an event handler configured to capture images from a scanner. As each event is processed, I'm adding the image onto a thumbnail UI control. However, unless I put a message into the event handler, the UI is not refreshed until all the images have been processed. 

I've tried forcing a refresh of the UI component and the form it is contained in, but that does not work.

How can I force a refresh of the UI ?

Thanks!