Error on submitting amounts over $1000 to Payment Express using Payment Express payment gateway

Using the PaymentExpress payment module, any amount submitted over $1,000 was generating an error (Code: IU) using the PxPay service. The attached patch replaces the affected code. The original code formatted the number with a comma included. The DPS gateway only accepts decimal-formatted numbers without commas. I have updated the code to remove the comma from the number before passing it through to DPS.

I have not confirmed this to be an issue when using the PxAccess service.