This must be simple I'm sure, I'm just not a programmer :/
any help or links please? thx
A 'quick fix' could be to set up an autoresponder at the address the form contents are sent to. This will probably be limited to a simple 'Thank you, your order has been received' message - depending on your email client, it might be tricky or impossible to include the order details in it.
The only other way that springs to mind would involve modifying the formmail script to add the features you want...