I was wondering if there is any way to do the following!

I need to have three text boxes, user will enter a number in each box.
Then i have four buttons, add, subtract, divide and multiply.
When i click on each button, the numbers in the first two text boxes should match the answer in the third text box. ex. (first box has a 4, second box has a 4, and the third box has an 8. if i click the add button, i should get a "correct" answer in the div below with a green background and if i hit the multiply button the div should say "wrong" with a red background.

Sorry but I'm a newbie to this and this is so confusing!

This is what i have so far.
Code HTML4Strict:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<script type="text/javascript" src="main.js"></script>
<title>Untitled Document</title>
<style type="text/css">
* {margin:0; padding:0;}
#resultdiv {}
<body style="background-color:#000066">
<input id="firstnum" type="text" size="20" />
<input id="secondnum" type="text" size="20" />
<input id="thirdnum" type="text" size="20" />
<br />
<input onclick="DoNums(1)" type="button" name="mybutton" value="Add Numbers"  />
<input onclick="DoNums(2)" type="button" name="mybutton" value="Subtract Numbers"  />
<input onclick="DoNums(3)" type="button" name="mybutton" value="Multiply Numbers"  />
<input onclick="DoNums(4)" type="button" name="mybutton" value="Divide Numbers"  />
<br />
<div id="resultdiv" style=" background-color:#CCCCCC">RESULT HERE</div>
Code JavaScript:
// JavaScript Document
// main.js
function DoNums (operations) {
	var fnum = document.getElementById("firstnum").value;
	var snum = document.getElementById("secondnum").value;
	var result = 0;
	switch (operations) 
	case 1:result = parseInt (fnum) + parseInt (snum);
	case 2:result = parseInt (fnum) - parseInt (snum);
	case 3:result = parseInt (fnum) * parseInt (snum);
	case 4:result = parseInt (fnum) / parseInt (snum);
	default:alert("invalid operation");
	document.getElementById("resultdiv").innerHTML = result;