What does "turning EIP on or off" mean? Edit in Place is an action you take - you edit in place, select a location, and it descends to that point. I don't see that there's anything to turn on or off?
Perhaps you mean toggling the display of the EIP surround? (As on the Options->Display form). If so, the trick would be to look at:
Figure out the relevant property name (I can't check because I'm sending this from a PDA in an airport), and then your bindkey would be:
Where "thePropName" is whatever it is called.
But of course this is guesswork - you may be asking a different question!