Third Party Photon CAS code example.

Does anyone have a code example for changing a RoomProperty in Photon using CAS, that includes the error handling?

I have a float[] as a custom property. The various players can change elements of the float array. However, because of concurrency, while I try to change one element, another player may try to change a different element.

Ultimately what I am looking for (psuedocode)

ChangeRoomProperties()
{
ReadRoomProperties() //casting them to an array[]
alter the desired element
recreate Hashtable
room.SetCustomProperties(prop, oldvalueProp);
if error == incorrect oldValueProp
{
ChangeRoomProperties()
}
}