MarkA
Head Pro
I was thinking the same thing myself Doon.
If the guy is good enough to move up the ladder the boss will know this, and if he can't afford to keep him I doubt he would begrudge him the chance of moving. I wouldn't expect too much time off though.
Honesty is always the best policy imo.
Always start negotitions from a position of power ie with another job offer, that way you'll find out exactly where you stand and if things don't go for you, upu can walk away knowing you've made the right decision. Why tell the boss about an interview though????