While waiting for a response, I found "in_solid", so I tried using it to detect whether my marker boxes were inside walls. When it didn't work, I copied and pasted the example from the manual and replaced my player's action code with it. I still don't get any response to show that it has detected a wall when my player touches one.
Code:
while(1)
	{
		 c_move(me,vector(time_step*10,0,0), nullvector,0);
 	  if (in_solid)		// Is Entity inside a block?
 	  {
 	    error("Solid!");
 	  }
    if (in_passable) // Is Entity inside a passable block?
 	  {
 	    error("Passable!");
 	  }
 	  if (on_passable) // Is Entity on a passable block?
 	  {
 	    error("On water!");
 	  }
		wait(1);
	}