Document content only locally visible

Hi

The "real" solution to my problem would be if it would be possible to view a part of a word document contact ONLY when the document is opened on a certain network. Or when it recognizes a certain path or link to a document.
The reason is that some knowledge in the document should defintely stay INSIDE the company. But it would be very usefull when the employees see it when opening the document.

Is there any good practise to approach this problem. Or is there a buildin solution for it.

there is such position as Document Controller.
Let him control which documents.