this can be very easily done by not adding the Local Checkout server behavior on the confirm page.
The local checkout server behavior is the piece that sends the transaction to the payment gateway.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.