Shopping cart integration

I have a flash site linked to a shopping cart. I can create a profile and buy items from the site and cart and submit payment over paypal fine. But after the transaction goes through the cart generates an error message that payment was not processed and the order does not get created. I do recieve the funds from paypal but the cart still generates this error and does not create the order in the system. I would like to have this fixed in one day. It the person can fix this problem then I will disscuss other things that need changing as well and will pay for these services separately. I need this done fast and I need someone that knows what he/she is doing.