Show difference between first and last column in a matrix instead of sum

Hi AnkitKukreja 

The table is named "Fakturarader"
The Rows are named "Leverantör"
The Columns are "FakturaÅrMånad"
The Value  is "NettoSum"

Not really sure what you mean by sharing "sample data". I have dragged the Matrix to the Desktop.

And the Matrix you have in my original post.