Please describe your use case some more, please.
The Splunk alert UI offers a dropdown to select "hourly" as a run interval. How does that not meet your needs?
@richgalloway I want to set up an automated alert on the report , i guess we can use cron expression but not sure how
The alert definition menu has a dropdown for the run interval. The last entry in the dropdown lets you specify a cron schedule for the alert. This is a set of 5 numbers, number ranges, and/or number lists that tell Splunk when to run the alert. I won't go into a full description of cron, but you can visit https://crontab.guru for assistance with generating a cron schedule.