You really need to select VNAV for that.
Level change just goes up at the selected speed at a thrust setting calculated by the FMC based on various inputs (like temperature and cost index) and goes down at flight idle at the selected speed.
In VNAV the FMC will do a bit more work for you. Say you are in the cruise at 30K, and you have programmed an arrival with an altitude limit of 5000 feet at a certain point and a speed limit of 250 knots below FL100. Provided you gove it the right wind information, the FMC will calculate for you at which point you start the descent. Provided you select 5000 in the MCP it will reduce to flight idle, descent to FL100, reduce speed to 250, and continue the descent to 5000 all at flight idle. This is a VNAV speed descent, which could be done manually with LVL Change to 10K, a speed reduction to 250, and a lvl chg to 5000, but that would be harder work.
Another option is the VNAV path descent. Say you are at 10K, and you have selected a point where you want to be a 5K. Based on the ground speed the FMC calculates the required rate of descent. What you do is select 5K in the MCP and the aircraft works it out for you. You could do the same by using V/S. You select 5K in the MCP and dial up a certain ROD. The FMC dsplays a green arc to show the end of the descent, and you adjust the V/S to put this arc over the waypoint with the 5K restriction.
All this assumes you can plan your own descent totally. In reality, unless you go to some remote island without radar, this is hardly ever the case and ATC will dictate your descent and speed.
Marcel, ref your question about N1 setting.
When you reach acceleration altitude (see my previous post) you don't only select 210 knots (or whatever you use on the day), you also select N1 on the MCP. This reduces N1 to climb thrust, which is calculated by the FMC.
Hope this helps.
Gerard
Ps: Marcel, waarom al deze vragen?