Как вариант...
<!DOCTYPE html>
<html>
<head>
<title>test</title>
<style type="text/css">
</style>
<script type="text/javascript">
function Go() {
var str=document.getElementById('data').value
var a=str.split(' ')
var o=document.getElementsByName('group')
var i
for (i=0; i<o.length; i++) {
o[i].value=a[i]
}
}
</script>
</head>
<body>
<div>
<input type='text' name='group' />
<input type='text' name='group' />
<input type='text' name='group' />
</div>
<input type='text' id='data' />
<input type='button' value='Set' onclick='Go()' />
</body>
</html>