Can not add a Monitor in Device template of VMware Virtual Machine ?

Can not add a Monitor in Device template of VMware Virtual Machine ?

Hi, All, 

I want to monitor the hard disk space for all my VMWare Virtual Machine using Device Template, but I can't .

OpManager Help (build 9200) says ...

"Device Template: The VirtualDevice template can only be applied over the ESX servers or Virtual Machines. This template is different from device type. 

Category: Category is VirtualDevice, which cannot be modified."

Is there any method to do this job?

Best Regards,

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