It may require a small amount of hand code curently, but it can probably be done. I'd have to look at the original code to tell you the best technique.
Most likely it would work if you just:
1) create a new page to add the item to the cart... make it a blank page, the reality is the page will never actually be shown, so you could even remove all of the <html>
2) add a recordset to the page with DW. Have it return the items you want added to the cart. In this case use the "simple" recordset view and choose the filter option ot fiter bassed on the passed url parameter strrecID.
3) apply the "eCart->Add to cart->add to cart from recordset" server behavior to insert the returned row into the cart.
4) set the redirect in this interface to go to the view cart page you create using the eCart display manager in order to continue to the checkout process.