Hello,
The solution is to modify this behaviour in the code, file:
\CMSModules\Ecommerce\Controls\ShoppingCart\ShoppingCartOrderAddresses.ascx.cs in the method
ProcessStep find the following code:
else
{
ShoppingCart.ShoppingCartShippingAddressID = ShoppingCart.ShoppingCartBillingAddressID;
}
... here you can customize it.
Best regards,
Martin Danko