Setting the margins of a RichEdit Control

Does anyone know how to set the margins of a RichEdit Control at runtime?
(i.e. I have a page(s) of richtext and I want to click on a button (for
example) to set the margins of the richedit to some specified values) Also,
how do I control the margins at the top of the richedit on printing?

Your assistance is greatly appreciated..

James Tallent