There isn't an API for the chart tool unfortunately.
I remember looking at that years ago and I think I recall noticing that it was storing it's data using the XML node stuff you can find in the AIXMLElement.h & AIXMLNameUtil.h headers. You can use that to look at the metadata node attached to a document. Like I said, this is all very vague even in my own head, but I thought I remembered seeing it stored in there; you might try creating a chart and then seeing if you can find the data you enter inside that metadata. If so, you might be able to reverse engineer out a way to automatically inject data into a chart.