Set the row height of row i+1 according to the difference of the active sort column values between row i and row i+1. That is, the bigger the gap, the bigger the visual gap has to be (although you are still free to calibrate the gap rules as long as it is visually consistent, you should minimize vertical scrolling, i.e. don't use too much whitespace). of course, only apply this row height feature when the active sort column contains numbers.