I don't think you can do this with a regular Gantt Bar, since Gantt Bars require a continuous dimension to be drawn along. However, based on your data it looks like you have one cell per week, and for that it should be possible to create a calculation and then use a Highlight Table to color the necessary cells.
Thanks a lot, your solution works for me. Only one thing from my snapshot I can't reproduce in Tableau:
I do splitting by year, month and week. So I need to show Labeled values of SUM for all filled cells which are nearby. Would be brilliant if I can even chose a range of filled cells for which I want to show SUM. Is it possible? See attached.
Thank you again!
values_of_filled_cells.png 9.1 KB