This blog will help you to build the Drill Down sample chart in SCN without using VLOOKUP function.
The drill down chart http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/50c39190-62c0-2e10-7ab4-82128be893fe?QuickLink=index&overridelayout=true&52239688287750 is a very nice example by Sirisha.
Here I have used two combo boxes instead of one. One is hidden. Here I have pulled the background and the components to be in the front and the combo box2 is hidden behind. You can find the attached txt file. Please change the extension to zip and you could find the swf and xlf files.
Please check the properties and highlighted areas of the xcel file to get a better understanding.