Custom field populated by User list

Custom field populated by User list

I need to add a custom field that will be populated with the name of a Zoho user. I'd like to use the user list as the Related List, just as it is used in the Lead Owner field.
 
 
Is there anyway to do this?
 
Creating a pick list of users seems like a very backward way to do this and would mean duplicate maintenance of users when there are changes.
 
Thanks.