Retroactive Change Primart Flag Work Relationship

Summary

We want to change primary flag Work Relationship in the past

Content

We have an employee with 2 Active Assignments in 2 different Work Relationships in a multiple assignment enviornment: 

- Assignment 1 (Primary Work Relationship from 15/02/20 to 19/08/20) 

- Assignment 2 (NON Primary Work Relationship from 15/02/20 to 19/08/20, PRIMARY after 19/08/20)

We want to terminate on 31/07/20 the assignment 1, but it is not possibile because the assignment 1 is Primary on 31/07/20. So we would like to Change the date were change Primary flag on 31/07 to terminate the assignment. How can we change primay flag in the past? 

Version

20C