Assignment change Approval - Grade and salary only

Summary

how to trigger approval process only when there is a salary or grade step change

Content

Hi all,

i have a complicated requierment to make approval flow for assignment change.

the issue is that i need to send it to approval only in cases which the salary Or grade / grade step are being change.

(other cases will go to self auto approve)

any ides?? 

Note - there is another issue which i already solved --> because grade step can appear more than one time depend on the grade and the grade ladder i need to have a lot of grade step combination.