In the Start menu you will find the XPression Studio SDK help file.. This shows the basic API of available commands etc..
In the beginning of it you will find some examples to help show how to put some of the commands together, but there are more for external API applications as opposed to the internal scripting.
The scripting language is VBScript, so you can google for tutorials on VBScript to get a handle on the syntax of the language itself. Most people start by just copy/pasting existing examples and learning from those..
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