Box trigger needed

hello i need a new trigger done for me. Can someone give me a layout on how to make a box of choices? so like when you beggin the game a box pops up and asks you what race you want to be like...
[/center]Human
Nightelf
[center]Undead

Easily Done:
First We Set The Variables, Make A New Variable Called Race_Dialog and its a dialog variable,Next Make A Variable For Every Button Of Your Box, i.e. Nightelf_Button variable type is dialog button.

Event:
Map Start
Action:
Create A Dialog Button For Race_dialog Labeled Night Elf Race
Set Variable NightElf_Button = last created dialog button
Change The Title Of Race_Dialog to Race Seleaction (or watever)
Pick Every Player and All Players And Do Show Race_dialog for picked player

thanks... but like say i wanna pick night elf right... do i make a seperate trigger that goes like

Events
Dialog- a dialog button is clicked for planeswalkerpick (in my case)

Conditions
(Clicked dialog button) Equal to Urza

Actions
Units- create 1 urza for player 1 at location________

is that how you would add on to the thing? im confused

in wintermaul or w/e when you begin the game sometimes a box of choices pops up saying

electricity
poison
ice
etc.

and say you click electricity a spark would be created where ever


how would you make triggers to opperate like that?