ColumnNo() returns the number of the current column within the current row segment in a pivot table. The first column is number 1.
If the table is one-dimensional or if the qualifier TOTAL is used as argument, the current column segment is always equal to the entire column.
If the pivot table has multiple horizontal dimensions, the current row segment will include only columns with the same values as the current column in all dimension rows except for the row showing the last horizontal dimension of the inter-field sort order.The inter-field sort order for horizontal dimensions in pivot tables is defined simply by the order of the dimensions from top to bottom.
if( ColumnNo( )=1, 0, sum( Sales ) / before( sum( Sales )))