Help with Multi Row Formula tool

[HW1]

Could someone help me get the correct Multi-row formula?
I have a partial output as:

RecordID	Identifier	Amount
18
54
64	Y
65		37.5
66		40.5
67	Y
68		22.5
69		30.5
74		53
82
83

I want the sum of the above all values till the next "Y" in the [Identifier]

as:

RecordID	Identifier	Amount	Sum
18
54
64	Y
65		37.5
66		40.5	78
67	Y
68		22.5
69		30.5
74		53	108
82
83

I am trying the multirow formula tool with the logic "If [Identifier] is null, add all above non null columns from [Amount] else null but I am unable to get it right.

Help is much appreciated.
Thanks

[apathetichell]

If I may make a suggestion - it's easier to assign a distinct identifier to Y using a multi-row formula than to create a running total. So instead of summing here - have your formula say

if [row-1:recordid]=null() then 1 elseif [identifier]="y" then [row-1:identifer]+1 else [row-1:identifier] endif

Note - the first part tests for the first record and creates an initial value of 1. It looks at a column field which will not have any nulls() in the previous row unless the row is the first row.

Now - once you have this identifier add a summarize and group by that new column and sum your data.

[HW1]

Is this the formula tool or the multi row formula tool where I will attempt this?

[apathetichell]

multi-row formula tool. Anytime you are looking at a previous row or future row - you use multi-row tool.

[HW1]

I think You mean

IF IsNull([Row-1:Identifier])
THEN 1
ELSEIF [Identifier] = "Y"
THEN [Row-1:AMOUNT] + 1
ELSE [Row-1:Identifier]
ENDIF

I am getting 

RecordID	Identifier	Amount	New Field
18
54			1
64	Y		1
65		37.5	Y
66		40.5	1
67	Y		1
68		22.5	Y
69		30.5	1
74		53	1
82			1
83			1

Where am I going wrong?

[HW1]

There is no Row + 2 or Row - 2  else this can be an easier solution

[apathetichell · Accepted solution]

Not sure what your fields were called when I wrote it out so I actually used "identifier" the second two times to mean the new field - sorry. 

This is the proper formula:

if [row-1:recordid]=null() then 1 elseif [identifier]="y" then [Row-1:newfield]+1 else [Row-1:newfield] endif

[newfield] is the name you use for the new column.

Your [amount] column was non-numeric when I pasted it so the attached workflow does the multi-row properly and converts your [amount] field to a numeric field. Then it summarizes by different "y"s.

[HW1]

Oh good! I used your approach further to get what I want.

Thank you!