Create a parameter and set it to text. Just enter your above values, and you only need a single calculation that looks something like:
CASE [Parameter You Created]
WHEN 'Employee' THEN [Employee]
WHEN 'Org Level 1' THEN [Org Level 1]
WHEN 'Org Level 2' THEN [Org Level 2]
WHEN 'Org Level 3' THEN [Org Level 3]
WHEN 'Org Level 4' THEN [Org Level 4]
You're just turning a string input into a different field output. Add this field as a filter (and show the filter), and it should function exactly as you wanted. The user selects the level from the parameter, and the values in the filter update automatically.