I was just reading a nice guide to adding dependent data lists from existing data (State > City) on ExcelBuddy.
From the site: This tutorial will show you how to create a dependent list on Excel. This technique is extremely useful when categorizing data. In the example below, the user will select the State in cell A3. Cell B3 (City) will pull a city based off of the users selection (Read it now on ExcelBuddy)