A parameter gives a changing input a name. A local let binding is a useful way to practice that dependency: set the threshold once, then refer to it from a row filter or a reusable function. In Excel you can also manage parameter queries through Manage Parameters. Here you edit the parameter values in the Advanced Editor and see their effect immediately.
A custom function separates a rule from the rows that call it. Its arguments should include every value the caller must choose. Avoid hiding a region name or threshold inside the body when the next report needs a different one. These tasks pass thresholds and status values explicitly. The function remains inside the query for a portable local exercise; it runs again against the hidden extract, so both the dependency and the returned table matter.