Thanks again Harry.
So the Script should be;
var Timer timer = null
rule "gMainDoors CLOSED"
when
Item gMainDoors changed to CLOSED
then
if(timer !== null) {
timer.cancel()
timer = null}
NestTStat_away_mode.sendCommand("HOME")
end
rule "gMainDoors OPEN"
when
Item gMainDoors changed to OPEN
then
if(timer === null) {
timer = createTimer(now.plusSeconds(10)) [|
NestTStat_away_mode.sendCommand("AWAY")
timer = null]}
else
{NestTStat_away_mode.sendCommand("HOME")}
end