Clearing validation upon change

I am trying to create a spreadsheet with the following functions:

Clear the validation boxes in column M, when the value in column E and/or Column G changes.

When the value in Column E changes, change the drop-down choices in Column M with the building parts applicable to that building.


Lists, tables and "helper" cascading dropdown boxes are on the work sheet "Lists".

Not sure if the request is clear (or even possible)