Automation for loop

I need help creating a for loop via automation or possibly a java script page.

I have accounts which have multiple commission as their child records as well as reps as their child records. In other words, every account can be shared by multiple reps. When a commission is generated I need to create a sub commission for each of the reps related to this account. The ideal way would be if automation would have an option to generate a record for each of these reps. Based on my knowledge, this is not an option as of yet. Can anyone guide me how to go about this maybe with a custom javascript page etc.

Thanks in advance