How do you create multi-level, linked, combo-dropdown boxes for drill down selections in Excel?

Help me please . . . I am creating a form and I need to be able to create drop down list that change the reference in a lower-level drop down list. For example - if the user picks a type of food (i.e. American, Tai, Oriental, Italian, etc.) the the next drop down box should list retaurant chains that server that kind of food (so if they pick "American" this selection box/drop-down list would list Denny's, McDonald's, Hardee's, etc.) and then the third level would list the street addresses for the restaurant chain they chose (i.e. if they chose McDonald's it would offer 123 North Main, 1782 Terrance Ave, etc.). I figured out how to create the controls/combo boxes and link them to a range with the value's I want offered, but how to you do the logic for the 2nd and 3rd levels so they know what list to refer to??? Thanx, DLK