If you only want a task to run if another task was run successfully:
This way you could schedule task01 every 30 minutes, and then have a chain of tasks that get triggered depending on the outcome of that task.
There is also a "On multiple events completed" trigger if you need a task to depend on several other tasks.
Sorry for the confusion - prob. wording of my origan question.
As an example :
TASK A Runs every 30 minutes
TASK B Dependant on success of A
TASK C Dependant on success of B
IF B fails then obviously C will not start. However in 30 minutes time I don't want task A to start until I get a chance to investigate the cause of task B issue.
maybe something like this:
Set up a supporting task (QMC > System > Supporting Tasks) that runs every 30 minutes. It could be a "Pause" task with no delay.
Then on Task "A" have a trigger "on Multiple events" which runs on success of the above "Pause" task and Task "B" and "C" in the last 30 minutes.
You probably need also a daily trigger or similar to get it to run the first time.