Newbie Project

I am sure this will be simple for you guys, but I am still a beginner. I am trying to create a basic keypad simulator for my kids kindergarten class to practice entering their lunch codes. The pad is very simple. Numbers 1-9 and 0 with a clear and an enter button. I have the number buttons appending their corresponding number into the LCD dynamic textbox using the following code.

on (release){
LCD.text+=1;}

Question 1: Using the clear button, how do I clear the LCD dynamic textbox.
Question 2: Using the enter button, how can I have the movie check to see if the numbers entered are correct based upon a list of numbers in a text file?

Thanks any help you can provide.