Converting your patient encounters should be possible, because Amazing Charts uses Access databases, and Excel files are easy to convert to Access databases.
However, this is something that Amazing Charts Technical Support would have to accomplish for you. I think Carlos would be the guy to talk to.
Let us know what they say. If they say they can't help you, there may be a Plan B.
By contrast, converting your old patient demographics and insurance information is simple, and there is a utility in Amazing Charts to convert an Excel file that way.