refining: multiple terms per facet

When you select a term from the Guided Search of a taxonomy facet for say a vocab called "Topics".... it refines.. OK.
Now if you wanted to refine again from that same facet, you can't unless there is a hierarchal relationship with the existing refined term.

But if I am using the same vocab "Topics" to assign many unrelated topics to the nodes (multiple select), I need to be able to refine with more than one term for that facet.

Is there a way to make this possible? (I don't want multiple select at the guided search, just the possibility to continue refining at the next load)

Thanks!