Validating the Validation (Data Dependent Drop Down Lists)

Hi,

I've inherited a data template which incorporates a number of data dependent drop down lists. Unfortunately due to the limitations of data dependent drop down lists (can be circumvented via copy/paste and/or drag down) the majority of returns I receive contain errors which I then have to identify and correct. Is there a formula I can use that effectively checks that the options selected are valid? The attached spreadsheet shows a smaller example of the data I'm working with. The actual data drops down to 6 levels.

Thanks in advance,

Snook