Accessing more than variables with JavaScript

I find using JavaScript to work with variables in Storyline very useful but I would love to be able to do more.  For example I want to add a "thermometer" showing progress through rather a long course.  I did it on an old programme made with Presenter using Flash (and of course I am now avoiding using Flash to make the programme tablet friendly).  What I would like is to be able to access in JavaScript the slide number and the total number of slides then be able to output the length of a vector graphic (ie the mercury of the thermometer).  The alternative is to do it all by hand, slide by slide then prey the client does not ask me to add more slides or take some out.  Any chance any of that is possible either now or in a future release?

Thanks

Charles