What you really want is to create a graph 'on the fly' whenever a user requests the page.
If I were you I would look at a component that can do this.
I'm doing sort of the same thing in the application I'm building right now.
I use a COM componten to draw a graph. This component is called csDrawGraph and can be found at www.chestysoft.com
There are also other ways to do this. For example the Office Web Component
Here is an article about it. And another one.
Try searching the web. You will find usefull articles about it.