How to block access to the Grades for a leader in the merit and promotion plan (Grade above his own)

Summary: When the leader accesses the merit and promotion plan, he can select which grade is proposed in case of promotion, in which case we would like to block the leader's access to all grades that are above his own.

Content (required):

As a process all leaders in the organization are invited to open the merit and promotion plan and make adjustments. 

Merit (when there is only salary adjustment)

Promotion (when there is salary and position adjustment) and for this case mostly there are adjustments related to grades. 

These grades must be entered by the leader, who can only do so if the grades are lower than his own.