OMG! You are brilliant. Thank you so much @Christiaan_Huizer ! This has been bothering me for the past 3 days 
Hello guys. Is there any non-complicated, O(n) (n means number of rows) solution for this now?
Ander’s solution seems reasonable.
Hey Ken, welcome to the Community!
The most performance-saving approach would be to calculate the “previous row” and store it into a lookup cell not by a column formula but through an action (i.e. fired once when the button is explicitly pressed, not recalculating every time when anything changes). With actions you are in control of what gets calculated when and in which order. This works the best when you are appending rows to the end (i.e. don’t need to recalculate any previous row) or insert the rows in controlled places (i.e. you can figure out the only other row whose “previous row” reference you have to update)
1 Like
I Try to use formula to get previous row for some items
but it give me error ( broken refernce) in col Prev NO c
i use new col Prev NO with AI to fix it and get the right refence from broken one
can ypu help me to fix this fromula