Hi. 'On a certain button clicked' type events will be true throughout the event sheet for the tick that it is true for that button, so all of those will execute in order.
Arranging them like so should work, assuming that 'ChoiceA' is zero by default:
[code:11fyr41t]On clicked Button:
Value "ChoiceA" equal to 0
b. Button.Set"ChoiceA" to 1
Value "ChoiceA" equal to 1
a.Write second Text
b.Button.Set"ChoiceA" to 2
Value"ChoiceA" equal to 2
a.Write third Text[/code:11fyr41t]
Then you may need to reset 'ChoiceA' to zero or something that doesn't apply to those conditions, afterward, depending upon your needs.
All of the 'ChoiceA' tests are sub-events of the 'clicked button' event, and the Else conditions make sure that only one is true per tick.
Tulamide made a nice tutorial on that subject a while back: Introduction to branching
That may help clear up the event logic for you.