Dictionary in Workflow Help

Anybody have a working example of using a dictionary in a workflow?

I am populating a dictionary in a For Each loop with Key and Value each set to string variables.  The Dictionary gets created as a Table (Dictionary to Table Activity).  I would like to be able to populate a List Box with the Values and have the output be the corresponding Key, so I can use it my query.   

Even just an example of a dictionary in use and how to retrieve values would be a step forward.

Thanks!!