access iframe content

i'm new to extjs. i have an iframe loading some content from the same context. as such:

{

xtype: 'box',

id: 'abcIframe',

autoEl : {

tag : "iframe",

src: "abc.jsp",

style: 'width: 100%; border: none'

}

}

later i have a button, and in i'd like to get access to the iframe document and elements in my javascript. any help is most appreciated.

thanks,

-mark-