web usage report filtering negative

Today my CEO asked to generate a monthly report about general usage of the Internet.

I'm working on SG125 with OS 9.601-5

As we are working with Office365, the top sites shown are hopefully related to Microsoft.com, sharepoint.com ..... but there is so much normal activity we have to go deep in the list to find what is not normal professional behavior.

I thought I could use the Filter option to select elements which are not normal but only manage to select positive filtering and not negative.

i.e. :

        - I manage to select "facebook.com" which list only facebook activity

        - I manage to select "twitter.com" which list only twitter activity

        - I cannot exclude "Microsoft.com" so I get facebook, youtube and any other "non professional" website... but all on a same list without Microsoft.com related activity

Is there any kind of regular expression I need to know to filter by exclusion?

Thanks for your feedback.