Altitude constraints with respect to a waypoint are very easy to enter in the FMC. I just enter ABC/75 (or -75 if before ABC) and that creates a new waypoint where i can enter the altitude resctriction. The rest will be done by the FMC (if within aircraft performance). If you say "reach within xxx minutes" or "at 0324" i have to do the calculations and fly it in the V/S-mode without any FMC-guidance. Everything for the B733 only, don't know about other aircraft types.
Denti