Excel 2007 : multi level dependent list

I need help with understanding how to add a third dependent list. The attached spreadsheet has the following tabs:

form = this shows the 3 levels that I need. Data Validation has already been defined for Levels 1 and 2.

values = values for each of the 3 levels

Guidelines/instructions I've come across have been helpful until it gets to explaining the 3rd level. I get that each name list has to be unique. One set of instructions suggested combining the entries in the first two columns, which didn't make sense. I then tried an 'if' calculation but the end result wasn't the full list -- just the first line entry. So I'm close but have hit a wall in figuring this out.

Any suggestions?

See attached.

You need to make a named range for each possible selection in preivious data validation.

To allow for items with spaces, you need to alter the INDIRECT formula used...

so the data validation formula for E2 is:

=INDIRECT(SUBSTITUTE($C$2," ",""))

You have to name the ranges in other sheet where the individual lists reside.

The named ranges should be the same as the elements you can choose in the 2nd validation and remove spaces between words.