[Xymon] Problem to graph disk % from DEVMON

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 !