Yes, but to do it with just one command you need to swap with the one at the bottom.
I see duh. But is there like a getnextLowestDepth? How do I know which one is lower.
No, there is no such method as getNextLowest... There is a getDepth() method of the MovieClip class that you can use to determine the depth of an object, so you might be able to figure out a function to get to the bottom of things using that. What you might be able to do is set the depths for the objects yourself so that you know what the lowest depth and range thereof is, and then use that knowledge anytime you want to move something to the bottom (also see getInstanceAtDepth() )
If you were to use AS3 this would be much easier.