Easy Dynamic textbox question

Alright I want to have a Dynamic kind of text box that is always there in my movie (movie is all on one frame). And I want to be able to edit the text that I want to display in the box through actionscript, such as like when a button is pressed then text changes to whatever I want it to.

Kind of like:

on (release) {
text == “blahblah”
}

Something like that, if anyone can help me code this I would greatly appriciate it! Thanks so much in advance.