Different theme per user

Hi,
I want to update the theme on my site. It is possible to have a different theme only for me? In this way I can test the news theme and my users show the regular theme when I’m testing.

I would to have something like this

<?
if ($user_ID == %MYUSERID%) {
call the new_theme
}
else { /* FOR ALL THE VISITORS */
call the old theme
}

Thank you!

?>