[development] how to run new .install on installed module

Hi, Probably a simple problem but I don't find solution on d.o. I have a D6 contrib module that did not use database before, but now it does. The problem is that even though a .install file has been added, the database is not created in case the older version of the module is enabled already, not even after running /update.php. http://drupal.org/node/323314 explains that ".install file is run the first time a module is enabled" -- but how to make sure the initial database is installed on an existing module? Is the only solution to solve it via hook_update_N, detecting whether the table exists, and installing it -- even though in fact we are installing, not updating? Thanks, Tomáš