I would like to populate the Affected Services based on input into a custom field

[Wendy Moulang]

I am trying to figure out if it is possible to populate the Affected Services field in a Change Management request with multiple values that a customer would enter when creating the request. 

I have done this previously with a custom watcher's field and the Jira Watchers, but can't seem to get this working. 

Firstly, does anyone know if this is possible and secondly, can anyone refer me to some reading material in this regard? I read something a while ago, (which was very helpful) but can not find the same/similar information now. I have searched!

Any help would be appreciated. 

Thanks
Wendy