Basicly your looking for a multiple-linked-dropdown-list.

See links on this item:

Create multiple linked dropdown list in excel
http://helpdeskgeek.com/office-tips/...ists-in-excel/
http://thefinch.wordpress.com/2008/0...datavalidatie/
http://www.contextures.com/xlDataVal02.html
http://www.snb-vba.eu/VBA_Afhankelijke_validatie.html also in Englisch