Do you have a workbook you've started on that you can post so we can better understand what you're looking to do?
I'm not sure that my workbook efforts to date will be of much help. But the data might be, along with some explanation. I have 800 items, each with a category of Buy, Hold or Sell. Buy and Hold items have no Sell Date (ie. Null value). Sell items have a Sell date in 2016, 2017, 2018 or 2019. What I'm trying to plot is the "walk down" from today; so 800 now; less 78 by end 2016, leaving 722; less 131 by end 2017, leaving 591; less 46 by end 2018, leaving 545; less 61 in 2019, leaving 484.
Right now, I'd settle for plotting the "end of year positions" but ideally I want to be able to have the ability to show end of quarter, end of month etc, depending on who's asking.
I have a data file ready to share, will look into how I upload it.