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

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.

sumif example.yxmd