Passing custom props from vapp to vms

Hi,

   I am fairly new to vapps, and have question around it.

   vapp (via OVF) provides way to specify custom properties which can be passed down to vms inside it.

   Now, there is OVF for vapp and OVF for individual vm inside vapp. And, I want property set on vapp to be connected to property on individual vm, so that setting it on vapp sets it on vm and I dont need to modify intenal logic of vm to read property.

   That way, vm can be dropped into different vapps and only change i need is external config to map vapp property to vm property.

Thanks.