Note 20: You can write custom Delphi methods that might be invoked in a template, by using the IOTACodeTemplateScriptEngine interface of the Delphi ToolsAPI. A complete example (the only I know of) is Daniel Wischnewski Google Search Template, which you can find at http://cc.codegear.com/Item/23866, while a description is on his blog at: http://delphi-notes.blogspot.com/2005/12/creating-script-template-engine-for.html.
This note in in Chapter 2, page 45. This blog post is part of my "113 Delphi 2007 Handbook Notes" blogging project, to promote my new Delphi book.