Hi Trung
it's a while now since you asked this question but maybe you (or someone else) are still interested in a solution.
**Please notice: This only works with Axon.ivy 6.3 and greater.**
You can find a demo project [here][1] which shows a pattern to create reminders to a task and destroy them if the concerning task is done.
![alt text][2]
At the To do step an expiry handling is defined as following:
![alt text][3]
The error start gets the task id of the expired task:
![alt text][4]
If the To do task is done before the remind task was, the Remind task will be destroyed:
![alt text][5]
The sent signal is caught by the attached signal of the Remind task:
![alt text][6]
Regards
Barbara
[1]: http://developer.axonivy.com/q-and-a-attachments/reminderPattern_63.iar/upfiles/reminderPattern_63.iar
[2]: http://answers.axonivy.com/upfiles/2016-10-11_16h06_00.png
[3]: http://answers.axonivy.com/upfiles/2016-10-11_16h06_12_goxvf2Z.png
[4]: http://answers.axonivy.com/upfiles/2016-10-11_16h06_28.png
[5]: http://answers.axonivy.com/upfiles/2016-10-11_16h06_22.png
[6]: http://answers.axonivy.com/upfiles/2016-10-11_16h06_39.png
