Coupons used on discounted items

We have a 10% special using a coupon and buy in bulk discounts appling to some products is there anyway to stop customers from appling coupons to already bulk discounted products?

There is this that could be altered to suit your needs? http://forum.opencart.com/viewtopic.php?f=131&t=30346

Thanks Man, but it doesnt seem to work with discounted products unfortuantly... For example if you were to select the buy in bulk and save here http://www.ozfarmer.com/ball-mason-pint ... ball-mason you get a discount for a bulk purchase then you still able to apply a coupon code to get a further 10% it cuts the margins mighty fine! If Q's mod could work on any item thats sold less than full price that is what we would need.