If you want to make the Assignment group variable read only on the Record Producer request form, then try an onLoad Catalog Client Script:
function onLoad() {
if (!g_user.hasRole('admin')) {
g_form.setReadOnly('assignment_group', true);
}
}
If you want to make the Assignment group field on the ensuing incident record read only, but only if the incident was created via (a certain) Record Producer, then make sure the Record Producer is populating a field on the incident record that is unique - otherwise unused, or contains a unique value. For example, in the Record Producer script have something like
current.contact_type = 'self-service';
If you either don't use the Channel field normally, or no one or no process would ever otherwise populate it with this value when creating an incident outside of this Record Producer. Then you can create an ACL or Catalog Client Script to only allow users with the admin role to update the Assignment group field on these incident records.
