Excel 2007 : Graphing

I am trying to put a line graph together. The problem is the graph is congested if all data is graphed. I want to give the user of the graph the ability to pick the data they want to view. I want to show the average gallons of fuel for all regions/offices and the gallons for an office from a drop down box in a line graph format. Please see attached. Any help is greatly appreciated.

Thanks!