We have created a Public group and we want only member in this group can create Account record nobody else and we dont want to create permission set. In this group we have users of diffrent diffrent profile.

I want to write a trigger so that once a status of my object changed from high to low priority field shoud be updated by Null and all the records which has peiority greater than the current record should be decreased by 1. 

I want to write a trigger so that once a status of my object changed from high to low priority field shoud be updated by Null and all the records which has peiority greater than the current record should be decreased by 1.