Thanks for posting this in the forums! That's a great question. Unfortunately, you will always need the IR Blaster, in order to control your a/v source with your onscreen remote. Your set-top box sends out an IR signal through the face. The IR Blaster then blasts the signal over to the Slingbox. This is how it is able to control the cable box. Without an IR blaster, you will not be able to control your a/v source. I do apologize for any inconvenience this has caused you. Feel free to reply if you have any questions or concerns.
Have a great day!
The Sling Moderation Team