MS Outlook - VB.Net - Logon using Different Username, Password

I am using MAPI in VB.Net to retrieve Outlook mail sent to a mail box.
For this I am using username, password stored in the database. If one username, password fails I would to login with different username, password.

Currently this is not possible since the username is getting stored. Any idea... how to do this with another username, password ?

Thanks in advance