You can create those individual modules as separate captivate projects and then can use Aggregator.exe (It is installed in the same directory as AdobeCaptivate.exe) to create an aggregated project with TOC.
Here is how you can achieve this.
Publish all your individual modules as swf's (from captivate) and then create a new Aggregator project and add all swf's to that project.
Then do a publish in Aggregator. This should do the work.
If you'd like a more customized solution, there is a 3rd party product for Adobe Captivate called the Launch Pad. This is an HTML page with a menu. Clicking a menu item displays a published Captivate .SWF in the HTML page's content DIV area. This way, you can organize multiple Captivate movies in a menu of sections/subsections as you desire. The HTML and CSS allow you to customize the page layout as you wish. Product information is at http://www.kcwebplaza.com/adobe_captivate/products/launch_pad
Thank you so much.