How to set arguments values not from user(using wizard), is it possible to do that?

Also, in a more advanced scenario, you could go as far as implementing your own gathering service, which must implement IValueGatheringService, and can be specified in the XML as:

<GatheringServiceData ServiceType="MyService, MyAssembly">

Did you look at Value Providers?

http://guidanceautomation.net/wysiwiki/default.aspx?topic=Writing%20Value%20Providers

Also, in a more advanced scenario, you could go as far as implementing your own gathering service, which must implement IValueGatheringService, and can be specified in the XML as:

<GatheringServiceData ServiceType="MyService, MyAssembly">