The ccm select -not_in_stack command pops
the selection set stack, setting the current selection set to the
difference between its previous objects and the popped selection set.
That is, the new selection set contains objects that were in the previous
selection set but not in the popped selection set. For example, if
the top of the stack contains objects {a,b,c} and the current selection
set contains {b,c,d}, then the current selection set after the command
is {d}.
About this task
ccm select -not_in_stack|-not_in