String to Number Problem

programming flash
1

I have a textfield problem. I created a textfield (for input) and wanted to make some calculations using entered numbers. But it recognizes the inputs as a string. For example;

listen=new Object();
listen.onKeyDown=function(){
if(Key.isDown(Key.ENTER)){

    trace(i+3); // i is the variable of textfield
    
}

}
Key.addListener(listen);

For the program above, if I enter 12 in the textfield and press Enter, result is 123, not 15. How can i make it to recognize input as a number?

Thanks…