Create a Dialogue Box in adobe Flash pro?

I trying create a dialogue box using Adobe Flash Professional. Basically when activating a trigger, a box containing the text show up and when you press a buttan show a new text and the other delete. I already know as remove the box and leave the player free, but I not how to create this button in flash pro, that show a new text and hide a other text.

Can anyone help me with this? And sorry for my English.

I would read up on doing this in ActionScript 3 (scripting language for your flash app), and simple call your AS3 functions from unrealscript.

Also take a look at the Scaleform documentation for UDK: UDK | Scaleform