Sounds like you want to limit the grid, but not based on security. No problem, here's what you do:
[System.owner/Administration.Account/Administration.Account_Company/YourModule.Company/Administration.Account_Company = '[%CurrentUser%]']
This path limits your grid to only items that have an owner with a company that is also associated to the current account.
Mendix already can keep track of the creator (owner) and last change details of an object. No need to create an association for that. Double click your entity on your domain model and turn on (at least) the Store owner checkbox
Create or change an access rule for your entity and switch to the XPath constraint tab. Click the owner button and Mendix will add the constraint.
Check here for more info: https://world.mendix.com/display/refguide6/Access+Rules