Hi Kim, not sure if the requirement is to have a selector based filter or just static condition based on some context value.
Here is how you can create custom filter if you need a selector based one - https://docs.kentico.com/display/K9/Developing+custom+filters
If you need just static condition based on context, you just add it to data source where condition
The relation in database is
- CMS_User (Employees) - CMS_UserRole (Role membership) - CMS_Role
So your where condition might look like:
UserID IN (SELECT UserID FROM CMS_UserRole WHERE RoleID IN (SELECT RoleID FROM CMS_Role WHERE RoleName = 'SilverPartners' AND SiteID = (SELECT SiteID FROM CMS_Site WHERE SiteName = 'CorporateSite')))