Add a resource to more than one department

Hi

We have set up departments to reflect our organisation but have recently added another department to give 3 of us greater contraol over a newly added custom field (we only want to allow 3 people the ability to amend the new field so that we have a degree of control over the closure of projects).

Is there a way to add these 3 people to the new department as well as their current department? Their current department is the one they actually work for. The new one is as a control method, if you like.

Thanks.