creating shift-click and ctrl-click buttons using javascript

I think even if you get the script loaded at the right time, you are going to run into issues with Captivate blocking the click for HTML5 unless you click outside of the presentation.

Are you using CP7 and swf, html or both?

Your syntax is a little off

$(document).click(function( e )

       {

        if (e.shiftKey)

        {

         document.Captivate.cpEISetValue('m_VarHandle.cpCmndNextSlide');

        }

       });

Also since you are using jQuery, you will need to load it for swf and for HTML5 you need to put the script after jQuery is loaded.