B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 174
Situational Awareness
Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
Human Factors; Procedure
Approaching Keating (ETG) on the MILTON 4 Arrival at FL390; we were instructed to descend to FL350 and cross ETG at FL330 and to give them a good rate to FL350.  I [verified] 350 in the Altitude window and selected Vertical Speed and 2000 fpm descent. I then [verified] 330 into the FMC for Keating. We leveled at 350 and I watched as the vertical RNP indicator approached the profile to start the descent to cross Keating at FL330. As it approached profile I selected VNAV but failed to put 330 in the Altitude window.  When the aircraft didn't start down I immediately put 330 in the Altitude window and selected Vertical Speed of 3000 fpm and speedbrakes but with only 2000 feet to lose we never caught up with the profile and crossed Keating 500 feet high.Better attention to details; however; when arrivals which are built into the FMC are altered by ATC which require intervention by the Pilots; a systemic potential for error is introduce into the operation.
My monitoring was affected by simultaneous tasks being performed while pilot flying was handling complying with ATC clearance. I probably should have temporarily abandoned the other duties and focused on monitoring duties only and resumed ATIS/OPC at a later time. Maybe; given our proximity to ETG and the small difference of altitude between both restrictions on this descent clearance; a choice to manage the descent ratio from 390 to 330 in a single shot instead of breaking it down into two actions/steps could have been a better course of action as well.
B737-700 flight crew reported they failed to make a crossing restriction when they missed a step in FMS setup.