You might want to try OWC (Office Web Components). Unlike MS-Graph, it's built as high-performance and multi-threaded. here's a link for the download:
http://www.auburn.edu/~brainsf/components.htm
>We would like to program a real-time Graph.
>In previous programs we've used the method thisform.line.
>What would you suggest. MsGraph or low-level functions,API calls,... ?