Attached is a solution for multilevel dropdown selections in Excel. The dropdowns are in cells B4, C4, and D4 based on your input table above.
I broke down the problem into several steps and used a few tricks up my sleeve so you may have to study the formulas carefully. I took advantage of a cool trick in Excel of being able to define named ranges dynamically. For example, in the Name Manager, see how I defined the range name “City.dropdown”, which defines itself according to the number of distinct eligible cities narrowed down according to what the user selects in the Region dropdown.
In the “Eligible Selections” in columns F-H, I used “zzz” to represent an item to be ranked last in columns J-L. Just make sure that none of your original inputs can possibly be sorted after “zzz” alphabetically.
Note that there are actually always an entry in the dropdowns for City and Outlet in cells C4 and D4. These entries may be incorrect according to what the user selects in the Region dropdown, so I conditionally formatted cells C4 and D4 to be font yellow and background yellow to indicate to the user that they should pick an appropriate City and Outlet.
Hope this helps!
P.S. It seems I cannot attach an Excel file in response to your post. If you tell me your email address I can email you the Excel file.