Loading library from name

Hi,

I have trouble to use a library that I load depending on a variable data.

$mylibrary = 'Custom_Lib';
$mymethod = 'Method1';
//those two are retreived from a database.

//After I use the method:

$this->load->library($mylibrary);
$this->$mylibrary->$method();

//I have an error that I'm calling a method on a non object...

I've tried also
class_alias(strtolower($mylibrary), 'useclass');
$this->useclass->$method($record);

//same problem...

Any one have an advise to call a special library/method from dynamicly ?

Thanks for your help,

Yannick