How can you enter a Rate Code Group on Job Data if the Default without Override is turned on?

Hi!

We have rate codes that are supplemental earnings which are percentage based. We only want the percentage to be based on the based annual or hourly salary (not any other rate codes). So I set up a Rate Code group called BASE with the standard NAHRLY and NAANNL rate codes. The calculation is working fine when the rate code is added to the employee at the Job Data level and the rate code group is assigned.

Ideally we want those rate codes to be set up with "Default without Override" so they can't be changed on Job Data. However, when I go to Job Data and insert a new row and add a new rate code (which has the "Default without Override" turned on) it defaults the percentage and then becomes view only before I can get the Rate Code Group field field set to BASE. So the percentage is calculated off all the rate codes, not just the base hourly or annual rate.