FadiHindi,
You cannot change the alarm configured for the object dynamically. However, you can achieve the similar results using a separate Alarm object.
In the Alarm object, the 'Signal' datamember would be your original object you want the alarm on. And for the HIHI, HI, etc., you can specify either contant values or other object like Pots and expressions that evaluate to a numeric value.
Hope this helps.
Regards,
Khalid