Image and Link Browser

Hi All, I have wrote my own personal image and link browser page using asp.net. The page BrowseServer.aspx is the same for images or links.

I need help to understand how FCKeditor exchanges data between windows. I have the following javascript function in my page:

function ExchangeData()
{
element = window.opener.document.getElementById("txtLnkUrl");
if(element != undefined)
element.value = document.getElementById("txtText").value;
window.close();
}

In this way, I can send the right value for the element txtLnkUrl but I need to know which is the right input to fill in. For the moment this parameter is fixed to value "txtLnkUrl". How can I understand in which pages the user click the "Browse" button and so which input field fill in the opener window?

I'm sorry for stupid question but i'm a javascript newbie.

Thanks,
Glenfinnan