You need to do a query to the database to update the setting in the setting table. You will need to this through PHP, if you don't know PHP or MySQL I suggest you learn and understand what is going on before proceeding with your product.

Check the "Articles" section for more information on these subjects.

Not only check the Articles section, but on Google for PHP tutorials, as they will provide more information on PHP/MySQL.

Thanks guys to reply,

I know php and mysql coding and i've build many products before but this is the first that i need cron to be used in a product. I'am just confused about what the meaning of "RUN A QUERY TO UPDATE SETTINGS TABLE". As is this settings table already exist as a part of vbulliten or i have to create? What is its name exactly? Also do i have to create a field in that table for each of the variables i want to pass its value to the template?

Sorry if it is still not clear what i want to do, but this is my best in english.
Regards,