how to crate cronjo not depending on user access

Have tried plugins for wordpress cronjob plugins

Cronjob Scheduler and SetCron are worthy a shot…

my personal favorite is Cronjob Scheduler..

with cronjob scheduler

Running your cron tasks
Most shared providers offer a crontab manager, or you can speak to your shared
hosting provider about setting up our cron job. If you manage the server, you 
can setup your cron using the crontab service. Make sure that wget is 
installed befor doing this.

Creating Custom Action Example
function my_cronjob_action () {
   // code to execute on cron run
} add_action('my_cronjob_action', 'my_cronjob_action');

courtesy wordpress plugins

regds..