Actually there is a way. The 722 has 2 independent outputs that you can use to watch 2 different programs simultaneously - make sure you are using the "Dual" mode. But there are a few catches:
- Main output (say OP1) is the only one with HD capabilities. OP2 is only SD. You can still watch a HD program but it will show only in SD.
- OP1 uses IR remote, OP2 uses RF remote. Slingbox uses IR.
So, the options are:
1) Use OP2 on TV, OP1 on Sling. You have full separate control on both devices and Slingbox remote can be used to control the receiver. Cons - You will only get SD on TV through OP2.
2) If you want HD on TV, you have to use OP1 on TV, OP2 on Sling. But as OP2 uses RF remote, you cannot use Sling remote but only the dish RF remote. So you will have to be in the same house and use Dish remote. Obviously this won't work if you are trying to use Sling remotely.