[Xymon] Problem to graph disk % from DEVMON

[L.M.J]

Hi,

  I'm retrieving data from a remote SNMP device through DEVMON : works 
fine and I'm happy with it.
  Now, I would like to graph the disk occupation en %. I retrieve SNMP 
Disk % in the column "disk" but I can't figure out how to create a 
regular disk RRD graph.
  I'm graphing others data from DEVMON with NCV, but I would like to 
build-in disk graph settings, can someone provide a simple syntax/conf 
example please ?

  Thanks !