Xlang10 is a script interpreter encapsulated in an ActiveX control. The Xlang10 ActiveX library is capable of expression evaluation, conditional logic, file and directory functions, and looping. However the real power is in the ability to add custom functions through method calls. When a custom function is encountered in a script an event is triggered, telling you which function was used and makes the parameters to the function available for retrieval and handling in your code. When you set the return value of your function, script execution resumes. There are events that allow a trace debugger to be built, variables to be examined or modified or other programmer actions to be taken. This is a complete scripting engine that is easy to use and has a powerful base scripting language. Help files in RTF and other formats are provided, documenting the base scripting language. You can simply add help for your application's extensions and you have a documented scripting language for your application.