db2 connecting to a db via alias and storing user name and password
DB2 won't store your username and password - neither the server, nor the client. What you could do is set up an ODBC setting in Windows. (I am assuming you are using Windows given you mention Excel, though I could be incorrect in that). The ODBC setting allows you to store the username and password on that Windows system. Do be careful with that though as Windows will warn you that the password isn't stored the most securely.