Not correct, Stan or Shaka. You can fly away from a selected altitude in the 737.
If you are in ALT HOLD mode at the preselected altitude, then select a lower altitude, which arms V/S, you can then climb at +6000 fpm, and the aircraft will attempt to hold that - NOT SAFE!!! Similarly, at 2,000 AGL you can select 3,500 in the Alt window and -1500 fpm in the V/S window and only the ground will prevent you going lower than 0 AGL.