running another plugin's functions

I'm trying to run a function from another plugin and wanted to know if this was how I should do it.

function update_permalinks( $args )
{
$blog_id = $args[0];
$switch = true;
switch_to_blog( $blog_id );
call_user_func(wpsc_clean_categories);
//do_action('admin_init', 'wpsc_clean_categories');

call_user_func(wpsc_update_page_urls);
//do_action('admin_init', 'wpsc_update_page_urls');

restore_current_blog();

return "Completed Action";
}

Basically I'm trying to work with xmlrpc and control the application remotely and i've got most of it working except this doesn't seem to be working, although I could be wrong. I've not thoroughly tested it.

Suggestions, comments, etc.. welcome...