I thought you had access to current volume , without needed to add up bars
If so, then all you need to do is
Take last SIZE, subtract from CURRENT VOLUME, and divide that new value by SIZE, to get the % increase in volume Im referring to.
Size last X minutes = 50,000
Current volume =200,000
200,000-50,000 = 150,000
150,000/50,000 = 33% increase in size over last X minutes
If somehow you don't have current volume as a single data point, then you'd have to calculate it. Not sure why this is any harder than the % price move scan already built in