Hyphen (-) in form value

I need some help to create a fuction to check a Hyphen (-) sign in a form..
like

if (form.value.indexOf("-")
{
alert("Invalid Value");
return false;
}
else return true;

Any help please......

 

Here's an example:

<script type='text/javascript'>
function checkInput(input)
{
	if(input.indexOf('-') != -1)
	{
		alert("Invalid Value");
		return false;
	}
	else
		return true;
}
</script>
<form>
<input type='text' value='' onchange='checkInput(this.value)'>
<input type='submit' value='Submit'>
</form>

Code (markup):

 

thanks brother.... i was really in need of this

thnks..