Help with list.sum formula (custom column) to finish data transformation

Hi

I'm kindly asking for the help to finish data transformation. I have done up to Add index column. My problem is to construct a List.Sum formula on custom column formula. See the attached excel sheet. if possible follow the step I have done so that I learn, if you restart the process I might not understand it, since I'm still learning Power query.

Thank you.

Regards,

Sunboy

Hi Bo_Ry

Thank you for the formula.

Regards,

Sunboy

Hi Bo_Ry

Thanks for the formula. It is working well. However, I have been trying your formula, when I reach COLUNM FORMULA stage, and I write this:
ABalance = Table.AddColumn(AIndex, "Balance", each
let f = Table.SelectRows(AIndex,(A)=> A[Customer Name] = [Customer Name] and A[Index]<=[Index])
in List.Sum(f[Debit]&{0}) -List.Sum(f[Credit]&{0})),

The formula says Error. If I copy and paste on Advanced formula editor, it works well. My challenge is that I do not like to memorise formulas, because If I had a small change in my database, I cannot change the formula to suit the changes made.

Maybe I'm doing it the wrong way, if possible please explain.

Thank you.

Regards,

Sunboy