Hi Nick,
From above post I understood you wanted to Complete all related task when one of the Task is completed by user.
This can be achievable by writing Table Level Script on communication table.
1.Script will read the current communication record and its created date.
2.Based on current communication record and its created date, program will read Communication Link records that has same Created Date. (When a Task is created for 3 different users it sets the same created date and time for the related tasks.)
3.Now, on Update Record function in TLS, as soon as current communication is set to Complete, script will fetch the data as mentioned in point 2 and update their status as Completed.

Hope this helps!

Regards,
Dinesh

I've never written a table level script before. Where can I start?

Hi Nick,

You can refer the below links from the community site to get an idea about the Table Level script

https://community.sagecrm.com/partner_community/b/hints_tips_and_tricks/archive/2008/03/03/an-example-of-a-table-level-script-showing-update-of-data-not-submitted-from-browser.aspx

https://community.sagecrm.com/partner_community/b/hints_tips_and_tricks/archive/2009/05/22/using-a-tablelevel-script-to-update-submitted-values.aspx

Hope this helps!

Regards,

Dinesh

Did you figure out how to do this in the end?