How do I get info from controls?

I’m trying to make a 2D opengl game. Now it would probably be alot easier just to do it all in code w/o messing around trying to make an editor, but I want to just because =). So I started messing around with menus, dialog windows, and controls and stuff. Well, I got a dialog window for creating a new area. Problem is, I don’t know how to get what was typed in the edit boxes. What I want to do first is, when the user hits “Create”, I want to check the width and height boxes to make sure they’re integers and are >= 1. This is mainly just a test. I might not even finish the editor (or the game)… in fact I probably won’t because I have a terribly short interest span =). But I just want to know how to do this heh. So any help would be appreciated. And thanks in advance. =)

A good reference about such subjects is the book openGL Game Development