I have a Deal with a bunch of Associated Custom Objects
(sub invoices). Due to a migration all the sub invoices got created at the same time. I made a “custom_created_at” field because i cannot overwrite the original created_at field.
I want the deal to property sync the most recent sub invoice based on the custom date
Hi @RaymondSnow, I hope that you are well!
Great question, thanks for asking the Community!
I have found a similar thread that you might want to take a look at.
The solution from @Olivia_Bagnall on this post “Workflow that copies the date of the most recent associated custom object record to company” might give you ideas.
Also, I’d love to put you in touch with some of our Top Experts: Hi @Olivia_Bagnall, @GreyHamilton and @deepikaverma do you have suggestions to help @RaymondSnow, please?
Have a lovely day and thanks so much! 
Best,
Bérangère