if you use ADO, see
http://www.able-consulting.com/ado_conn.htm?f=ado_conn.htm#ODBCDriverForOracleFromOracle
oConn.Open "Driver={Oracle ODBC Driver};" & _
           "Dbq=myDBName;" & _
           "Uid=myUsername;" & _
           "Pwd=myPassword"
oroConn.Open "Provider=OraOLEDB.Oracle;" & _
           "Data Source=MyOracleDB;" & _ 
           "User Id=myUsername;" & _
           "Password=myPassword"