normalized volume

[KrishTrader]

Hello,
I need help regarding Normalized Volume. I don't know how to write a script for this in ThinkorSwim. Please help.
Here is the detail:

Normalized Volume = (Volume/50 day average of Volume)*100

if the norm. volume > 125 is high volume
if the norm. volume < 80 is low volume.

 

[Joshua]

declare lower;
plot NormVol = (volume / average(volume,50)) * 100;
plot HighLine = 125;
plot LowLine = 80;