Passing Custom Directory username and password via URL in Ajax

[#1]

Does anyone know the syntax for passing the username and password for Custom Directory users to open a QV document without an Authentication Required prompt in Ajax?  I have tried the following without success:

http:\\QVServer\QvAJAXZfc\opendoc.htm?document=QVDocument.qvw&host=local&ntname=myusername&password=mypassword

http:\\QVserver/QvAJAXZfc/opendoc.htm?document=mydocument.qvw&host=local&userid=myusername&password=mypassword

Both these still give me the Authentication Required prompt.  At that point, myusername and mypassword work just fine.