I don't know. I do this all the time (though it's his secretary who takes care of it). It isn't a big deal to her anyway. She's been known to call me just to let me know an opening has come up even when I didn't ask her to do so. Does it make you feel too needy? Think of it this way: if you were trying to get in to see any doctor or dentist or whatever and they were booked, would you hesitate to be asked to be placed on a waiting list to be called in case of an opening? It's a pretty common practice.