You can create a list view using Virtual machine as the subject and add the parent cluster property. Then create a report with that view in it and depending on where you run the report you will get a list of all the VMs and the cluster they are in. (choosing vsphere world will show all VMs regardless of the vcenter, Select the vcenter to show all Vms managed by that vcenter and so on)
You may need to export the report as an excel sheet and modify it if you want to list each cluster but should be easy enough.
I am not sure how or if you can block them up in vrops.
