Change x axis scale mid graph on timeline

Hello,
I"m using excel 2003 and I"m making a time line of the old testament according to the bible. I've got a pretty good start. However I realized that I want my to change my scaling midway through my graph, because I"m finding that people lived a lot longer way back when. So from my graph start to about 2200 BC I want the X axis to have a major unit of 500 years and after that I want to zoom in and have the rest of the graph have a major unit of 25 years.
I currently have split them up into two different graphs. I would like to combined them into one. I was trying to do it by adding the right graph on a different series and on the secondary x axis but I could not get it to work. Could some please help me out? Or at least let me know if what I want to do is possible.
Thank you
timeline.JPG