Thinkorswim is TDA/Schwab's trading software.  There are plenty of things that the vanilla settings don't let you do, so the platform has many places where you can view the code behind how something works, and rewrite parts of it to better suit your needs.  It's done in a proprietary language called "Thinkscript", similar to Java (what thinkorswim itself is written in).  

Below are examples of scripts I have written either for clients or for my own personal trading use.  Click on any of them to view the syntax used and screenshots of how it works! 

*Note:  All custom scripts shown here are to demonstrate my experience with Thinkscript, and are intended for educational/informational purposes only.  Not investment advice, or a recommendation of any security, strategy, or account type.  We recommend that you study the Thinkscript Manual and Thinkscript Tutorials prior to utilizing any custom scripts in your own trading, to have a better understanding of the code you are using.