Textinput help

1

Hi! Im new here. I have 2 textboxes. T1 and T2.

If I type a number in T1, it will automatically add +10 and flash in T2

Ex. 2 - 12

listenForEnterObject = new Object();
listenForEnterObject.onKeyUp=function(){
		voca_pg2.text=parseInt(voca_pg1.text)+10
    }

Key.addListener(listenForEnterObject);

My question is, what to do if I want to type in textbox2 and nothing will happen in T

Ex. if I type 4 to textbox1, textbox2 will become 14 right.

I want to edit 14 and change it to 5 so it would look like:

4 - 5

I’ve tried

voca_pg2.onSetFocus = function(oldFocus) {
Key.removeListener(listenForEnterObject);
}

but I need to use listenForEnterObject again later again so removing it is not a good idea.

Plus I have a back and next button

button1.onPress = function() { 
	voca_pg1.text=parseInt(voca_pg1.text)-10
	voca_pg2.text=parseInt(voca_pg2.text)-10
};

button2.onPress = function() { 
	voca_pg1.text=parseInt(voca_pg1.text)+10
	voca_pg2.text=parseInt(voca_pg2.text)+10
};

it looks like 10 - 20
20 - 30

How do I make it block so it would not pass negative numbers when they click back button a lot?

Help and suggestions are greatly appreciated. Thank you.