Free shipping over a certain amount

hi,

I have a problem setting a 'Free Shipping' coupon code that only triggers when items in basket total over £60.

I've currently got a this working but without the over £60 part. Everytime I enter this part as instructed on the help videos the discount coupon works for any amount in the basket whether under or over £60

Current code below. What do I need to add to make the trigger work?
Would appreciate any guidance on this.

//eCart Rule
function WAEC_oj_uk_08_FreeWorldwideShipping() {
$totalDiscount = 0;
if (true && ((sizeof($this->Items) > 0) && ((isset($_SESSION['PromoCode'])?$_SESSION['PromoCode']:"") == "SANTA") && (time() >= strtotime("11/26/10")) && (time() <= strtotime("12/21/10")))) {
$totalDiscount += $_SESSION['shippingAmount'];//Result
}
return WA_eCart_FormatNumber($totalDiscount, $this->ForceDecimalsC, $this->DecimalPlacesC);
}
//eCart Rule


Thanks/
G