Agent Selecting Multiple Dispositions (or Subject/Categories)?

Content

Is it possible to set up the Subject, Category and Disposition Menus to act as a list that the agent can check multiple that apply? In our call centers there are often more than one driving factor we'd like to track.

I have discovered the  List Box control in the Workspace Editor but only acts as a triggering mechanism and isn't committed to any saved tables. Trying to be clever I used the List Box to "append Text" to a custom field but I have been unable to restrict the rule to only appending once for the same option (if the list is checked and unchecked it reappends the text) and I'd need 1 Workspace Rules for each option I'd like available in the List Box and I haven't even imagined how I'd approach decoding the results of that field.