A quick search of the Poser Python forum turned up these 2 threads.
http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2080793

In ockham's post, save the attachment (looks like a broken image link) as a .txt file and then change it to a .py extension for a figure shadows on/off script.

Or this thread http://www.renderosity.com/mod/forumpro/showthread.php?message_id=2710897  for a script from mason (you will have to copy the code and make the script yourself) for a script which will do it also.