Dropdown menus with filtering?

Hi

Please help me on this puzzle!
I work in a venue and currently arranging a spreadsheet to help maintanance. We have two columns (A & B). We are after both columns to have dropdown menus for users to select from.

I am currently using data validation in column A (a dropdown menu). Once the user makes their selection in column A, they will then move onto column B to select the location. It is in column B I need to have only those locations available to choose from. Hope this makes sense.

I have added an example of what I'm after. Please help me if you can

Thank you! YohYas