Overlapping line charts

I think this would be a bit advanced but if anybody could possible do it and give me a price for it that would be awesome.

So here's the scenario. I have two different line charts that are on the same X axis scale (post date) and a different Y axis scale (1-100 vs 500-1000). I would like to be able to make those two charts overlap in order to compare the trends. I was thinking this might be possible if you could allow for a different X axis to be set for each field you have in the chart thus making it so that even though the values are on a totally different scale they would come up in the same area allowing you to compare the trends along the same date range.

This is lower priority to some of my other feature requests but if anybody is interested in doing this for under $1000 let me know.

Thanks.