The Pro-HD has a built-in TV tuner, so if you just connect a coax cable from your wall to the input side of the Slingbox, but do NOT connect a coax cable from the output side of the Slingbox to the coax (RF in) connector on your TV, then the TV channel should not change when the Slingbox changes channels.
So, then, how would you get a signal to your TV so that you can watch it independent of what the Slingbox is doing? The answer is to put a two-way signal splitter on the coax wire coming out of your wall. Then connect one of the output connections on the splitter directly to the coax input on the Slingbox, and the second output connection on the splitter directly to the RF IN on your TV. Then both the Slingbox and the TV will receive the signals independently from the wall outet for your cable TV service.
Note, however, if you are using a cable box between your wall and your TV, and this cable box controls all of the channels that you receive, then you cannot watch all of the channels controlled by your cable box independently on both the TV and on the Slingbox. To watch all channels in that instance, you would need to rent TWO cable boxes from your TV service provider.