Script to pull cumulative vol after hour from a day ago?

[Thebtrader]

My script isn't working. Any ideas?

def afterclose = Gettime() > RegularTradingEnd (20200508);
def beforeStart = GetTime() < RegularTradingStart(20200509);

def vol = if afterclose and beforeStart then vol[1] + volume else Double.NaN;

plot PreMarketVolume = vol;