Register an even to run a function every time a document is saved

Hi

I´m was looking in the Illustrator JavaScript manual..but did not find this kind of information. Can you tell me if I´m missing anything obvious?

I have a function and would like to run this function every time the user invokes the process of saving the active document.

For example, the script is running. If the user go to File > Save or File > Save As, then... Illustrator invokes the function "x" in my script;

Is it possible? Where I can find information on how to register events in Illustrator?

Thank you very much

Gustavo.