The VCS User Guide includes a full "VCS event triggers" chapter. Here is the relevant resfault trigger part:

Description
Invoked on the system where a resource has faulted. Note that when a resource is faulted, resources within the upward path of the faulted resource
are also brought down. This event trigger is configurable. To configure this trigger, you must define the following:
TriggerResFault: Set the attribute to 1 to invoke the trigger when a resource faults.

Usage
- resfault triggertype system resource previous_state
- triggertype—represents whether trigger is custom (triggertype=0) or
internal (triggertype=1).
For this trigger, triggertype=0.
- system—represents the name of the system.
- resource—represents the name of the faulted resource.
- previous_state—represents the resource’s previous state.

To enable the trigger
To invoke the trigger when a resource faults, set the TriggerResFault attribute to 1.

> But where do i specify the other required paramenters like :

The arguments are provided by VCS while invoking the trigger.

> Futher i could limit this action to one and only one resource in the service group am i right ?

You just need to filter in your custom code.

Regards

Manuel