Validate proposed salary/salary changes against information stored in the Org EIT

Summary: We have 120 LE's. which have Org EITs where salary ranges for state and local (min/max) are stored along with the State/Local Jobs info. This State/ Local Job information in the EIT matches with the position name. (We don't have Grade rates).

So for example, when we do a salary change, for John Doe who is in the "Controller 1" position right now, we want the system to 1- Identify the LE to which John Doe belongs, then match the "Controller 1" position title with the State/ Local Job and then validate the new salary against this state and local (min/max) are stored against corresponding the State/ Local Job. We are unable to see any way to fetch EIT information in the object or field validation rule. Kindly suggest!