accessing form controls in another form

Question

I have a outer skin page ( say mainpage.aspx) which contains controls like label and textbox.
I am  useing  another page (say content.aspx) to display actual content of the page.
How do i access the outer skin page controls (example mainpage.aspx label control) in content.aspx ?
doing something like this but throwing error
mainpage obj= new mainpager()
Label mainlbl = (Label)obj.Form.FindControl("prodlbl");