[mishnas]

What I need is an additional variable for the time-and-sales window that can calculate the difference between the actual buys and sells that have accumulated over 3 time periods giving me a positive or negative total for each time period (similar to the bid and ask difference available in Sierra but calculated for the actual sales).

I need the time periods to be easily changeable by typing a number in one box (e.g. 30 minutes, 15 minutes, 3 minutes etc) with the results appearing in an adjacent box for all three time periods chosen.

That's it. And if you can help much strength to you!