Epicor 10 Posting Rules

I’ve been tasked with customising the shipping / invoicing process of Epicor 10.1.600.

They’ve asked for some custom fields on the customer shipment entry for pallet quantities/shipping costs which transfer across to custom fields on the first line of the invoice for the pack. That’s the easy bit.

For the steps they want to happen next they’ve provided an on screen walk through. When the group posts, a GL journal is created and each invoice creates an entry posting the shipping cost to a specific account. Once the group is finished the journal is auto balanced against another account.

The obvious method to achieve this for me is for a service connect workflow to mimic the on screen step provided.

It’s also been suggested to me that this can be achieved by creating a posting rule. This sounds like it should be a good fit for the task but I’m struggling to get started with it. I’ve got the technical reference but it doesn’t really seem to tell you how to use it, I feel I’m missing the initial understanding of the building of custom rules to be able to use the technical reference.

Is anybody able to point me in the right direction for custom posting rules?