PSA - Resource - Group Of resource

Hi,

In Psa I want to create a group of resource.

I mean for example 2 people are oblige to work in the same team. 

If I book Book Mister A, Mister B should be booked because they always work together.

then I want to group them in a kind of package/team but The TEAM AB should be bookable only if Mister A and Mister B are available. If One of them is not available (because working in another project or on holiday) the Team AB is not bookable.

Mister A can also be in a team AC and Mister B can be in team BD each team can be booked on different project

I have seen on resource, that I have the group type. but after I don't know how to link contact or user resource to it

can you help me ?

Many thanks