[BETEPAH]

или

<form action="" method="POST">
	<input id="m" name="">
	<br>
	1. -
	<input name=""><input name=""><input name=""><input type="button" onclick="add(this)" value=" + ">
</form>
<script>
var count = 1;
function add(btn) {
	var parent = btn.parentNode;
	parent.insertBefore(document.createElement('br'), btn);
	parent.insertBefore(document.createTextNode(++count + '. - '), btn);
	parent.insertBefore(document.createElement('input'), btn);
	parent.insertBefore(document.createElement('input'), btn);
	parent.insertBefore(document.createElement('input'), btn);
}
</script>