Load a .HTML, modify it and insert on a iframe?

Well it's pretty difficult to explain my problem.

I'm currently developing a toolbar for google chrome (extension) materialized by an iframe. This iframe is as you know a HTML file, but self hosted (I mean it's a local file). Basically this file construct a basic toolbar, so what i need is to load this file, and modify it by adding some components like buttons,... Then when i've made the change i need to sav开发者_开发百科e this file to then load it on a iframe. But i have a LOT of issue to do that, i can't find a solution to do that...

Hope someone can provide me some help !

This answer may help:

Can't write to dynamic iframe using jQuery