C# Fill Web Controls - Need Some Help

ello,
i have small browser (c# ) with a webbrowser control.

and a button fill login:

that button fills the webform with my login details:

for example is working good for my mail on yahoo, i don't need to write the username/pass... just click fill and then click on login ( haven't yet succeeded to click from c# )

but on other websites i have some problems because they use an popup ( iframe/ frame with the input fields....).

for example http://www.yellowpages.com/ i can't fill the login form.

i tried:

HtmlElementCollection tagsCollection = getCurrentBrowser().Document.Window.Frames[0].Document.GetElementsByTagName("input");
foreach (HtmlElement currentTag in tagsCollection)
{
currentTag.SetAttribute("value", "eureka");
}

but i can't pass the "0x80070005 (E_ACCESSDENIED))"

i really, really need some help.


Thank you!