Generating Allocation formula with percentage of source to target account

Summary:

Hi Experts,

I have an client requirement where they are allocating 5 percent of total balance form source departments to target departments. Target parent department have around 300 child departments .As we can not add parent department in target in formula rule , how to write allocation formula for target parent department instead of adding all 300 child departments in Formula rule.

23C (11.13.23.07.0)

Thanks,

Pavithra H