Order of posts alphabetically

[Cyn]

In forumdisplay.php I have the following code placed to alphabetize the thread titles in one forum.

switch ($sortfield) {
case 'title':
case 'lastpost':
case 'replycount':
case 'views':
case 'postusername':
case 'voteavg':
break;

default:

if($foruminfo[forumid]==163) $sortfield='title';
else $sortfield='lastpost';
}

This is placing the threads in reversed alphabetical order Z - A. How can I change it to place them A-Z? Thanks!