How do I force global to take a styleid after browser detect?

[vBMechanic]

I'm detecting mobile browsers and I want to force them to use the mobile style. Here is the code structure:

< application configuration >
-- browser detection:
Mobile user? Set styleid=2
Not a mobile user? Do nothing

< load vBulletin global.php >
-- Set styleid according to application's request



I'm assuming I should not have to modify global. After I detect the browser, I've tried a few different ways to force it, such as:

$_REQUEST['styleid'] == '2';

or

$styleid == '2';

or

$codestyleid == '2';

But nothing I set seems to affect global. It proceeds as if nothing was set.

Help?