Finding A Row Number...

[Aitch]

I'm sure this is simple - but I can't get anything to work lol

Column A has a row of numbers covering a range - 1 to X

What formula will find the row when the values start from 1 again - so I can get the row where the range ends?

For example below:
1st range is 1-4 so I need the Row of the value 4 = 4
2nd range is 1-3 so I need the Row of the value 3 = 7
3rd range is 1-2 so I need the row of the value 2 = 9

1	=Row number 4
2
3
4	<<< 4
1	= Row number 7
2
3	<<< 7
1	= Row number 9
2	<<< 9
1

Thanks for any help!

 

[Aitch]

Oh, I hate using Array Formulas as it seems to drastically slow down the sheet when recalculating - is that normal?

 

[Fluff]

Depends on how many rows you are looking at, if you use whole column references then they will definitely slow things down.