Slicer selected with one fixed AND one optional values

Hi everyone,

I have a list of events, which are grouped by the departments. However, some events are interesting for all departments (=cross dept.). In the slicer I have each departmant and cross dept. How can I have the "cross dept." always selected and additionaly any selection of users, so that they can see the events of their departments and also the cross department events.

Thanks for any help and suggestion.

BY