I have a very similar need and I have not found a solution yet. So far I've been able to create a scheduled task that STARTS the process on the day and time I want, and then a second task with a task event trigger that starts a refresh task every ten minutes when the first completes successfully. But there doesn't seem to be any ability to make the second task STOP. I've even set up code in the associated QVF that it will cause it to fail when I want it to stop, but the scheduled task will continue to run at each scheduled interval even if it is failing.
If you make any progress, I'd love to hear what solution you come up with.
In that case you'd need to create a new qvf and add your condition in scripting.
If you have a load table in DB, and if all the rows in DB table are complete then run the task, upon it's success it will kick start your 2nd task and if the Event Trigger fails, your 2nd task will not start.
Assigning dependencies for both the task.
1. Event Trigger1 qvf file to check (based on your condition)
2. Event Trigger2 to start upon success of Event Trigger1.
It works for me in Qlikview but I wrote a code to check with the DB to satisfy my condition. My condition is basically looking for fresh data and DB has designed a special view just to load the table if data is loaded if not it will fail.