Cascading Dropdowns that clear old selections

I have been working for the past few days on a tool that I can use at work that can quickly determine the lengths and widths of sheets of metal by using cascading dropdown boxes. The ultimate goal is to create a universal tool that is accurate and can be used by anyone, especially newcomers to the company. I have the spreadsheet close to what I want, however my limited knowledge of excel macros is keeping me from completing this task.

As the spreadsheet stands, I have used static (ie indirect()) dropdowns to select the end conditions of the metal sheet. Vlookup() is then used to find the necessary length that go along with the conditions selected from the dropdown. The only major step left is that I would like the secondary dropdowns to clear once the initial dropdown is changed. Another option would be a button or command that would reset the dropdowns to start over again. Under normal situations, I would just use guides to teach myself how to accomplish this, but the guides assume only the most basic situations (ie the dropdowns being right next to each other).

Attached is the current version of the document. It contains the instructions on how to use the tool. Feel free to toy around with the file to get a better understanding of how it works. I'm open to any suggestions.


Metal Sizes Dropdown.xls