How can I create a cron job in Magento without defining <run><model></model></run> in the XML?

I have a lot of jobs that need to be changed programmatically and we couldn't defined all of these jobs in the XML as these need to be dynamic.

So far, this insert the job in the magento cron, however, there's no run/model defined:

Mage::getModel('core/config_data')
                ->load(self::CRON_STRING_PATH, 'path')
                ->setValue($cronExprString)
                ->setPath(self::CRON_STRING_PATH)
                ->save();

How can I create a cron job in Magento without defining <run><model></model></run> in the XML?

I have a lot of jobs that need to be changed programmatically and we couldn't define all of these jobs in the XML as these need to be dynamic.

So far, this insert the job in the magento cron, however, there's no run/model defined:

Mage::getModel('core/config_data')
                ->load(self::CRON_STRING_PATH, 'path')
                ->setValue($cronExprString)
                ->setPath(self::CRON_STRING_PATH)
                ->save();