This can be done pretty simply by using the code: (setvar "clayer" "Layer1") where "Layer1" is the name of the layer you want to switch to.
A simple routine to do this would be:
(defun c:layer1 ()
(setvar "clayer" "Layer1")
To activate the command and switch to Layer1, you would just type Layer1 at the command line. This command will only work for this layer though. You would need many of these routines for every layer in your drawing. Is there some reason why you want to work this way, instead of using the layer list box on the "Layers" toolbar?
You can also use the MATCHPROP command, to select an object and match it's properties to another object, or just select the object and then choose the layer you want to move it to, from the layer list box on the "Layers" toolbar.