Inactive grades associated with active grade rates

Summary: Our company created all new grades. We associated the new grades to current jobs, we inactivated the old grades, and need to end date the old grades on the grade rates. Is there a way to do this via a load? We do not want to inactivate the grade rates as the new grades are still associated with them.

Content (required): We have not successfully been able to remove the old inactive grades from the grade rates and need to understand how to do that via a load. This is causing issues with reporting and we need to find a way to clean this up ASAP.