Frameset with CodeIgniter

[eluser]Unknown[/eluser]
I know that frames are evil, but I need to port over a tool to CodeIgniter and this tool uses frames.
Firstly, I'm new to CodeIgniter so I might just be missing something very simple.

What I have is a controller which calls a view called main_page. main_page.php uses the frameset tag to divide the page into two frames. I have set the src attributes of the frames to be something like:
src = \"" . site_url("/controllerName/functionName1") . \"" and
src = \"" . site_url("/controllerName/functionName2") . \""

functionName1 and functionName2 represent the functions in the controller that call the view files for each frame.
The code for each function is something like this:
function functionName()
{
$this->load->view('view_file_name');
}

The url helper is loaded in the constructor of the controller.

The page gets divided into the frames correctly, but I'm getting a 404 Not Found error for each of these frames- "The requested URL /projectName/index.php/controllerName/functionName was not found on this server".
However, if I try loading the same URL (localhost/projectName/index.php/controllerName/functionName) directly, each frame shows up correctly.

I thought that this might have something to do with the URL so I tried changing the src attribute to src= \"" . baseurl() . "index.php/controllerName/functionName" . "\" but this just showed me a completely blank page.

Does anyone have any ideas about what I'm doing wrong? Or is it something about code igniter that will prevent me from doing something like this?

Thanks!

[eluser]Unknown[/eluser]
I got it to work, but I had to manually include the entire link in the src attribute:
src = http://localhost/projectName/index.php/c...nctionName

I haven't been able to figure out how to get it to work with the url helper though. Any suggestions?