Custom Installer/Datasource configuration: Login

Hi,

when I create a custom installer, I can store the login ceredentials to the datasource (RDMS) within.
Either I can store it, or I can set it to prompt upon login.
What I cannot do is to let the user enter it only once.
What I'm looking for is to ask the user only one time for his username & Password, and then store it in the datasource configuration.
I don't care that much whether this is asked during RDM client isntallation or if there is a checkbox "Save values" when starting RDM Client and it's prompting for the user/pass.
This would simplify the installation process.
Even better would be if I can preselect RDM features (custom, complete etc) and license agreement. But this is minor. User are used to say yes to everything. Mainly I want to prevent explaining them how to click themselfs though to enter their user and pass for the datasource.

regards
Alex