Thanks for using our answers forum. We would be more than happy to assist you with the issue of setting up the PRO-HD to allow different channel viewing.
All you would need to do is use a splitter where the cable comes out the wall. Run one end of the splitter to the cable box, and the other to the Slingbox. You will be able to use the component or composite cables to the cable box, and the Slingbox user will use coax. This will allow you to view 2 different channels. In order to set up the Slingbox to view the coax, you would follow this article below.
Hope this helps!
THe Sling Moderation Team