Variable that points to a library class?

[eluser]JackU[/eluser]
How can i do this so it works? I wan´t the $myservice variable to point to the loaded webservice.

if ($message=="a")
{
$this->CI->load->library('webservice_a');
$myservice = $this->CI->webservice_a;
}
else
{
$this->CI->load->library('webservice_b');
$myservice = $this->CI->webservice_b;
}

$data = $myservice->loadstuff();