Single field fits fault category, event category determined by group of faults

Hello,

Attached is a sample spreadsheet - sample07APR2010.xls - that contains data from 2 events in Sheet1. Each event may or may not be comprised of multiple faults. Each fault fits into a category on its own; however, if an event contains a certain group of faults (which may or may not be in the same individual fault category), the event category is something else. For example, the first event in the spreadsheet contains 30 individual faults of various individual fault categories. When pooled together, they make up a "Grid or power cycle" event.

How can I best organize the fault reference data (FaultCategories sheet), grouping where necessary? The other challenge is coming up with a lookup formula that determines the faults associated with the event, then assigning an event category. Also note that the faults grouped to make up an event category may change. Plus, new event categories may be necessary in the future.

Any help is greatly appreciated!

Thanks in advance,

SchoobsVT