ExcelRobot

/*
Name:  Multi-Level Dropdown Validation (MultiLevelDropdownValidation)
Description:  Returns the list of allowable values for a specific cell based on 
   the entries to the left.
Parameters:
   tablename - name of the Excel table containing the data validation dropdowns.
   header - table header cells from the first column with data validation to the column for which
      to return list of values allowed.
   keylisttable - reference to dynamic range containing the MultiLevelKeyLists lambda key lists table.
Source:  Written by Excel Robot, inspired by Wyn Hopkins (https://www.youtube.com/watch?v=r0DTFodQYJQ&t=989s)