Username parameter in url problem

I have this web agent that takes a some parameters from a URL when executed. One of the parameters is username=.

When the username parameter is supplied in the url to the agent and the caller is anonymous (not authenticated). Domino prompts for a login and password. If the parameter is omitted in the url everything works as expected and the agent executes.

The parameters to the agent comes from an external system so I can’t change the parametername.

Is there a way to make domino not to think it should authenticate when the parameter is supplied?

TIA

Fredrik