SSRS Dynamic Data Source

Question

Dear Sir/Madam,
I would like to inform you that i am a very new user to SSRS. I learn the basic things and able to make the reports. I am using VS 2008 and BIDS. But i can't move further. I want to use the dynamic data source.  Let me clear my issue one by one.

1. First of all user should input four credential a)Server name b) database name c) user id 4) password. It will help to make the connection with database and make the data source. The credential should be store in session or cookie.

2. Now the user will be able to see all the reports without giving the credential because he/she already given.

I made a dynamic data source but the credential is asked for every time when i open a report.

It will be highly obliged if you kindly solve my issue and give me the solution as soon as possible. It will be highly appreciated if you guide me through a demo project or an article.