MikFreeD,
<html>
<body>
<form>
<input id="1" type="text" name="1">
<input id="2" type="text" name="2">
<input id="3" type="text" name="3">
<input type = 'checkbox' id = '4' name="4">
</form>
<img src="http://javascript.ru/forum/images/smilies/smile.gif">
<p></p>
<script>
window.addEventListener('DOMContentLoaded', function() {
var form = document.querySelector('form'),
input = form.querySelectorAll('input'),
img = document.querySelector('img'),
p = document.querySelector('p'), arr;
img.addEventListener('click', function() {
arr = [].map.call( input, function(i) {
return i.type == 'checkbox' ? +i.checked : (+i.value||0)
},0);
p.innerHTML = arr[0]+ arr[1] - arr[2] + 100 * arr[3]
});
});
</script>
</body>
</html>