Add user as a watcher based on custom field selection

[ferns]

Good Day all,

I have a request to dynamically populate the watcher field with the account manager based on a preselected client field. So if a ticket is created with client A selected, user assigned to client A as account manager needs to be added as a watcher.

The field is currently a cascading select field so when the ticket is created, client A is selected and Account Manager A is the only selection available to the ticket creator to select which is a mandatory field.

Is there a way to achieve this and if so what is the best approach? We currently have scriptunner and dynamic fields plug ins available.