How to set a storyline variable from a WebObject?

Hi,

I need to set a Storyline variable from within the JavaScript code of a WebObject.

What I need to do is to set a "completed" variable when the WebObject interaction completes, in order to abilitate the next button to go to he next page.

Is there a way to let the WebObject JavaScript code call the GetPlayer() function?

Or it is possible to call a user defined function from within  the WebObject JavaScript code (see http://www.articulate.com/support/storyline/javascript-best-practices-and-examples)?

Thank you very much for your help!