Pass a variable between a controller

[eluser]Taff[/eluser]
Is it possible (or advisable) to pass variables between controllers?

I have one controller which I am using to upload a file to the server.
After it has been uploaded I would like that variable accessible via my parse_csv controller so this is roughly what I have:

Code:

class Katalog extends Controller {

    function Katalog(){
        parent::Controller();    
        $this->csv_file;
    }
    function upload_csv(){
        $this->load->library('Upload');
        if ($this->upload->uploaded) {
        //Save $this->csv_file for future reference somewhere
        $this->csv_file=$this->upload->file_name;
        //load view with link to parse_csv
        }
    }
    function parse_csv(){
        $this->load->library('Csvparser');
        //grab the data we saved in upload_csv
        $file_name=$this->csv_file;
        $this->csvparser->parse($file_name);
    }
}

Sorry for the silly question, I can't find anything in the forum about it which is probably down to me being the only one who doesn't know how to do it.

Thanks for any help!
Taff