There actually may be a simple solution for your problem. The method I’m listing should not be too overly complicated because you already have a shared border with some contents.
Create a new page with frames. In the left frame, copy and paste the contents of your shared border. In the right frame, copy and paste the information from your main home page. Save the pages. You will save the frameset page that glues all the frames, the left frame, and the right frame.
Now, you want it so that any link clicked on the left frame will load in the right frame. Therefore, right click on your left frame and select Page Properties. The Page Properties dialog box appears. Click the pencil icon to the right of the text field for “Default target frame”. The Target frame dialog box will appear. Select the right frame from the graphic that is displayed in the “Current Frames Page” box.
That should ensure that all pages clicked via your left frame will load in the right frame. I hope this helped, if not, don’t hesitate to reply back and I will try to see if anything else can be done.