Behaviour / Actions / Workflow

[AlexM]

Hello!
I have 2 tables: Quarters and Invoices
Invoices has column [Quarter] ref to Quarter table, so Quarter has [Related Invoices].

My goal is that at the end of the quarter to email all the related invoices to my accounts department.

On table Invoices I have 2 actions:

1. set on column [Status] - changes to “Sent” and then workflow (update) to send email to my clients
   So this one is done one by one - so far, so good

Now the problem:
2. set on column [Accounts] - changes to “Sent”

Where am I stuck?

I was thinking to have an action on table Quarter that somehow will run the action on column [Accounts] in the Invoice table for the [Related Invoices] of that quarter.

Once all the related invoices will have the column [Accounts] changed to “Sent”, then run a workflow that will send ONLY ONE email with all the invoices for that quarter attached.

Question 1:
How can an action on one table run an action on another table?

Question 2:
How can I include multiple attachments in one workflow based on having a column with the same value?
(here I am thinking will be a problem of synchronization too as the changes won’t be done in the exact same time - so probably a different solution needed)

Thank you!