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By configuring a cross-object field update with a workflow.
For every custom object and some standard objects, you can make activities where a change to a detail record updates a field on the related ace record. Cross-object field updates work for custom-to-custom ace detail connections, custom-to-standard ace detail connections, and a couple of standard-to-standard ace detail connections

For instance, in a custom recruiting application, make a workflow decide that sets the status of an application (the ace object) to "Closed" when a competitor acknowledges the activity. Or on the other hand, for standard objects, make a lead to change the status of a case from "Awaiting Customer Response" to "In Progress" when a customer includes a case remark.

Cross-object field updates are upheld for every single custom object that are offspring of custom objects in an ace detail relationship.