Vwap as Stop Mode Point

Hello Folks!

I am naive and trying to learn AFL, It been two days since I am trying to Setup VWap as Stop point but I am unsuccessful in doing it. Please help me to rectify it.

Bars_so_far_today = 1 + BarsSince( Day() != Ref(Day(), -1));
StartBar = ValueWhen(TimeNum() == 091000, BarIndex());
TodayVolume = Sum(V,Bars_so_far_today);
IIf (BarIndex() >= StartBar, VWAP = Sum (C* V , Bars_so_far_today ) / TodayVolume,0);
Plot (VWAP,"VWAP",colorBlue, styleThick);

Stop = VWAP;
ApplyStop (stopTypeLoss, stopModePoint, Stop );

Its not been executed during backtest
Please tell me my mistake
Thanks in advance!