is a generic function to calculate the difference between two indicators.
The default inputs are High and Low but in most cases you would use Custom Inputs.
For example, you could use the following criteria to screen stocks where the Close is within 1% around the Upper Bollinger Band.
% Diff. (Close BB Upper(20 2)) greater than or equal to -0.5
and % Diff. (Close BB Upper(20 2)) less than or equal to 0.5
((Input1 - Input2) / Input2) * 100