Pulling values from parent table custom field to child table custom field

[Tyler Johnson]

Trying to get a custom field from the pm_project table to a custom risk field on the risk table. I currently have a BR setup that pulls the data but it is a permanent sync. Is there a way to modify it that way it defaults to these items but can be changed and does not update the parent when they are changed. 

BR 

before 

update , query

current.u_department = current.task.parent.department;
current.u_department2 = current.task.parent.u_department2;

The above BR updates the fields correctly however every time you update the field and save form it will pull parent projects field values. Im trying to get it where it defaults to the parent values but can be changed and also does not change the parents values. 

is there a way to script this in the default value field?

[_ChrisHelming · Accepted solution]

Make it an onChange client script, or a before insert business rule so it's not updating every time or only updates when one of the fields changes or is empty.