You shouldn't get your install hook to run updates. When a module is installed for the first time no updates should be necessary.
Updates are used when the module already is installed (the database or variables have been created). In that case, you don't want to reinstall the module as it will wipe all data, instead you create update_N hooks. Drupal will detect which updates are needed and those will be run going to
update.php. In Drupal 6 it will auto select which updates to do, but you can change it, while this is not possible in Drupal 7.
Drupal detects which updates are needed by saving the number of the last run update. This can be changes in the database, which will allow to rerun updates in Drupal 7. Rerunning updates is usually a bad idea and will most often cause errors and can in some cases mess up your data.
Always remember to backup your database before running updates.