I'd like to know how to access a control on another page.

I'd like to know how to access a control on another page.

Hello all:
 
I'm new to the forum and jquery, and I'd appreciate anyone's help if you can spare the time.
 
My question is this....
 
I have a page that by way of an iframe, it houses/hosts several other pages within it.  I would like to know when I'm sitting on one page, how I could change the value on another page's control using jQuery?
 
 
Thank you in advance:
 
Frank