Get grade rate differenttial from Job Requisition Object

Summary:

Get grade rate differential from job requisition object an set values to DFF in detail requisition section.

Content (required):

I Have an Autocomplete use case has a simple logic that is to get the value of the grade selected and set the values of two descriptive flex fields in the requisition details section. When the grade is filled into requisition, the rule must get the rate differential for this grade and set the mínimum and max value of the rate in descriptive flex fields.

I Didn't find a way to get this value from available related objects from Requisition Object. I Would like to understand what object has the values of rate differential that I need.