custom function for counting?

[bbrimberry]

I have a column like below in power query

so on row 1 -- I need a 1 there.
on row 10-- the next time I have start I need a number 2

and so on.

I assume this is a simple custom function, but never done anything like this at the row-level before.
null values should be nulls.

My plan was to use a custom function to count and then fill down the null values.


I would like a counter to start with 1 and then increment by 1 every time the word start was seen

 

[brawnystaff]

Restart numbering for each change in