How to create bmi calculator inside flash cs5.5 using actionscript 3.0?

I'm not very familiar with flash so this is my current problem to deal with. I've found some code but it's in actionscript 2.0, when i tried to run it in my project, it shows the following error.

Here are my errors: 1. Scene 1, Layer 'Layer 2', Frame 1, Line 6

1067: Implicit coercion of a value of type Number to an unrelated type flash.text:TextField.

2. Scene 1, Layer 'Layer 2', Frame 1, Line 8

1180: Call to a possibly undefined method on.

3. Scene 1, Layer 'Layer 2', Frame 1, Line 8

1120: Access of undefined property release.

var weight_BMI;
var height_BMI;
var BMI_FINAL; 
total_BMI=Number(weight_BMI.text)/(Number(height_BMI.text)*Number(height_BMI.text));

on(release){
    trace(weight_BMI.text)
    trace(height_BMI.text)
    trace(BMI_FINAL)
}

AS2 is very different from AS3. AS3 works by using methods (in the same way as Java, for example). See the code below as an example (note, you may need to edit/rename your fields to get it to compile)

It works by attaching a Click EventListener to your calculate button which when triggered it runs the calculateBMI method. This method then performs the calculation and prints the result to your text field.

var myBmi:TextField;
var total_BMI:Number;    

function calculateBMI(e:MouseEvent):void
{
    total_BMI = Number(weight_BMI.text)/(Number(height_BMI.text)*Number(height_BMI.text));  
    myBmi.text = String(total_BMI);
}

btnCalculate.addEventListener(MouseEvent.CLICK, calculateBMI);