Tom - file attached with my code which works - although is awfully messy.

Some times it seems to run an error so if you ever refine it please let me know.

The one thing i want to do is make it less sensitive - ie now the code requires the boxes to be in exactly the right position, whereas i would like to make it work a few pixels in either direction, as sometimes the boxes mysteriously move a little...

anyways, see attached.

cheers