Communicating between Documents

I am working on a Visual C++ MDI application that is limited to having only 2 documents open at a time. The two documents are supposed to be able to communicate with each other. For instance, I should be able to export text from one document's view to the other document's. In addition, if a line is highlighted in one document it should also be highlighted in the second document.

Does anyone know how I may access one document from the other as well as do the other stuff?

Thanks

Tesita:)