notepadd++ or any editor - custom autocomplete

I need to trigger a custom auto-complete when user enters a certain XML tag or XML attribute. I would prefer notepad++.

I know in plugins/API directory there are list of files which contains keywords for auto complete.But it will not be very useful as i need to trigger autocomplete based on certain keyworkds.

The list is very vast so is there any other way to do it ? Currently i use a HTML javascript page to render the list. But its not that fruitful.

I want the list to be presented when someone is actually editing the XML page.

Any workarounds ?

Thanks,