D20 Actionscript help

okay, for everyone out there who doesn’t know, a D20, is a 20 sided-die, and i’m trying to create one in Flash. the only problem is, i don’t know actionscript all that well, and i know what i want it to do, and i know most of the singular scripts, but i don’t know how to chain them together. :-/ Basically, what i want to do, is click on a Button symbol named D20Button, and have the computer randomly select a number between 1 and 20, intergers only, and display them in a dynamic textbox called D20. Any help with this would be greatly appreciated.