Automate reset of Selective Access

We're looking for a way to automate updates of selective access which would include:  1) clear all existing list member access 2) set new list access.    Would like to have this automated via an import action.  Current imports into Selective Access appear to only be acretive.  Importing NO ACCESS into User Role, reloading original ROLE and reloading Selective Access in a clunky workaround.