Validate number

Hi all. I would like to validate a number a user enters into my form. This number can be 5 or 6 numerical numbers or have 6 numeric numbers seperated by a dash with 6 more numeric numbers like so 123456-123456. How can I do this. I'm stumped on this one. Please help me.
Tracy

It would be better to show what you've tried up to now so someone can offer some pointers.

I actually have nothing. I can validate 5 or 6 numbers but the other one confuses me:(
Tracy

Here is what I have so far but it does not work. Can anyone help?

<script>

function validateCharge(theForm){

//VALIDATE CHARGE
if(theForm.charge){
if(!theForm.charge.value.match(/^\d{5}$/) || !theForm.charge.value.match(/^\d{6}$/)){
alert("Please input a valid Charge Account!")
theForm.charge.style.backgroundColor='pink';
theForm.charge.focus();
return false
}}


return (true);

}


</script>

<form method="POST" name="theForm" onsubmit="return validateCharge(theForm)" action="--WEBBOT-SELF--">

<input type="text" name="charge" size="20"></p>
<p><input type="submit" value="Submit" name="B1"></p>
</form>

/\d{5}|\d{6}(?:-\d{6})?/.test(theForm.charge.value)

/\d{5}|\d{6}(?:-\d{6})?/.test(theForm.charge.value)

No.

if (/^(\d{5,6})$|^(\d{6}-\d{6})$/.test(theForm.charge.value)) {

James (007) Bond: (to Bibi) "You get your clothes back on, and I'll buy you an ice cream."