Custom values for custom fields

[Worper1997]

Hi

We are considering using trellisDesk for the support.
I had a question is it possible to add a custom field and send the user using custom url so it fills the field.(Preferably hidden)
for example I'm looking into:
index.php?page=tickets&act=add&step=2&department=1&user_id=1234&username=test@example.com&account_type=100

3 things should be customizable in this scenario:

1. The department should be set in $_GET and
2. The custom fields should be settable
3. Optionally the fields should be hidden so the user can't mess with them.