On the BillTo.aspx page there is a function named SetCustomerDefaults that allows you to set any property on newly created Customers. This function looks like this:
Protected Overrides Sub SetCustomerDefaults(ByVal Customer As BirdDogSoftware.Interfaces.ICustomer)
.Taxable = True
.Residential = True
.SalesPerson_No = "123"
.Customer_Type_Code = "ABC"
.Terms_Code = "CC"
.Ship_Via_Code = "UG"
In the previous example, all new Customers will be set to Taxable, Residential, have the Sales Person # of 123, the Customer Type of ABC, Terms Code of CC, and default Shipping Method of UG. All properties on the ICustomer interface are available in this routine. For help finding properties available on ICustomer, please set the discussion on Reflector.