I have a process in my checkout whereby orders with a value over £750 get 5% discount applied. To do this I have a hidden promo_code field which has a value of 'bulkorder' if {order_subtotal_val} is > £750. This works fine until the customer amends the quantity in the cart to bring the subtotal below £750.
I have some script on the submit action (update cart totals) of the form to remove the promo_code, which works fine - however on refresh the form has a blank promo_code but the {order_discount} applies the removed promo code anyway. If I click the submit again the order_discount refreshes to 0 as expected.
A similar thing happens if I the increase the total above £750 - submitting the form adds the promo_code to the field but until I submit a 2nd time, the {order_discount} remains at 0.
Any ideas?