Excel Bet Rules - Trailing Stop

[itwasthisbig]

Hi, I want to place a trailing stop on a Lay order. The Bet Rules are something like
LAY TRAILING_STOP:TRUE STOP:3 STOP_PLACE:5
But the above will put a Lay order in. Do I need to create an unfillable back order with the Lay as an offset with trailing stop? Seems a bit Heath Robinson. Or am I simply getting the syntax wrong? Or, is this not possible?
Thanks in advance

[itwasthisbig]

My mistake. I need to do this another way.