Thanks for the response.
Yes, this is the chart widget for flexviewer, version 2.2, and I'm using ArcGIS Server 9.3.1. What I'm envisioning is the combobox would be populated with the names of the different layers from the REST services. In my case, it would be the layers 1. County & 2. Watersheds.
Currently, the tool does query the server for values, but this is to calculate the parts of the graph and is all declared in the tool's xml. I do not want to allow the user to choose different values to graph, because it would introduce additional complexity and confusion.
Thanks,
Doug