how to change ODBC data source during runtime

I use ODBC access to dozen tables. I try to change database ALIAS during
runtime but I cannot.I have one component DB : TDataBase with ALIAS property
set up during design time. This component has 'DatabaseName' property equal
to 'MyDatabase'.
All my tables have property 'Database' equal to 'MyDatabase'

After my app started I try to change ALIAS according to configuration file.
So, I do something like:
   DB.AliasName:='NewAliasname'
   DB.Open

Unfortunately , when I open any table, I see that it is still table taken
from old alias (data path is defined inside ODBC alias).  What should I do
in order to really change ODBC data source during  runtime ?

I would greatly appreciate any answer.
Marek.