API for Custom Sheet Design

Is there a comprehensive API for the HTML and CSS allowed on custom character sheets?  Often I find that improvements to my custom sheets can not be completed due to limitations imposed by Roll20.  One example is REGEX in text input fields. Also, I'm currently looking for a means to implement a spreadsheet like control in my custom character sheets that would allow players to keep track of in game spending and carried equipment.

The wiki has a lot of information, but I doubt its complete. <a href="https://wiki.roll20.net/Main_Page" rel="nofollow">https://wiki.roll20.net/Main_Page</a> The only way to do a spreadsheet-like control is through Sheet Workers (javascript). You will also find the sumRepeating script handy, for being able to sum up cells in a repeating section.