How configure disk space thershold

my problem is how to modify alerts to specific devices and device group the structure of the device is as follows ( I have a group of devices with an alert by default, this group I want you to change the threshold , now within that group there are devices Particles of whom want to receive alerts when they exceed a specified threshold without having to remove the general alert that I have by default because once I modified is useful , for this I performed the following steps .

1 - specific Disk Alert : I go into the device and then create a local copy that says " Create copy " , and then modify the threshold to my convenecia .

2- Alert device group : only I change the threshold.

When modifying the threshold in step 2 runs but the alert specific disk failure can not tell me that I 'm making use WMI

Cheers