problems performing a subtraction between two fields of a Pivot table

[Hermes]

I have trouble performing a subtraction between two fields in a Pivot table.
I want to subtract the Close and Open fields. With the purpose of being able to realize the graph that is shown in the figure.
But I get the message showing in the figure.
regards
Hermes

 

[Hermes]

I attached excel file. I need to add the rows of the field AcumuladoO consecutively to make the graph shown.
Thank you and awaiting your comments and guidelines

 

[Hermes]

Good morning everyone
Achieve target using Defined Names to take the data from a pivot table and performing multiplication with the help of the lower triangular matrix. All as shown in the figure.
Is it possible that a matrix of 20x20 with zeros and ones, make me so heavy the excel file?
I have not been able to reduce the size of it so I can upload it to the forum !!!!
Good morning
Hermes

 

[Hermes]

With the help of this macro I create the matrix

Sub GenerateMTI()
Dim F As Integer, C As Integer

For F = 1 To 54 'Weeks in the year
For C = 1 To 54
If F = C Or F < C Then Cells(C, F) = 1
If F > C Then Cells(C, F) = 0
Next
Next

End Sub