Not all dialog boxes are selectable. As for scrolling, vertical scrolling should come into play automatically as soon as the list of items exceeds the display area. Horizontal scrolling, I'm sorry to say, I've never been able to manage to get to work, although, in theory, if the text is longer than the width of the dialog box, then the horizontal scroll should come into effect automatically, like vertical scrolling does.

If you'd like me to be of more assistance, please provide the appropriate section of your code.