Populate or Update List for Data Validation

[Winon]

I am using Office 2007 and Vlookup, Index or Match wont work in my specific situation. I have uploaded my workbook with more detail on Sheet 2 explaining my problem, and I am sure someone will be able to help me with a very simple solution.

The only thing is that Sheet 1 is not constant as it may change in the number of items, lines, columns etc.

Thank you for your time and kind assistance !