Build in variable for approvals

So we recently purchased the Web Help Desk and we are trying to get it set up.  There are a few requests where we would like to add a table of approvers or query AD for manager to get the approver name. 

Here is an example.  We have a large number of Active Directory Security Groups.  Each group has a manager assigned to it. 

Example:

Auditing - Joe

Finance - Sara

Human Resources - Frank

Marketing - Brenda

I would like to have a request that allows you to select the group (in this case department) and based upon what group is selected it sends the approval to the associated manager/owner.

Has anyone done anything like this or have any ideas of the best way to do this?