hi
pdif will give what you ask.
the price difference over 120 minutes.
so if it was 10.00 odds 120 mins ago and now is 10.00 odds it will return 0.
but you do not know what happened inbetween the 120 mins.
the price could have incresed to 15.00 odds and come back down to 10.00 thus making it a steamer and drifter, the later been the most likely.
or it could have gone to 7.00 odds and back to 10.00 making it a drifter and steamer, the later been the most likely.
as for the refresh rate, the odds will be the same.
if you want to compare prices and movement, it might be better to use the maxbp_120 and the minbp_120, then compare them to the price now.
mcbee