Changing Source_no en masse

We would like to update the source number on a large number of web orders.  Looking through the forums and the impresario tables, it seems like I can run an update statement on T_ORDER, T_TRANSACTION, and perhaps T_WEB_ORDER.

Is it as simple as this? Or am I missing an important update.  Even better, is there an SP I can tap into to take care of all this for me?

Thanks!