With Slice, you can insert Active Forms with dynamic columns. To do that, you will need to tick the option Dynamic Columns while inserting an Active Form from Excel:

Slice is using a new funciton called TM1RptColumn that works in similar ways as the TM1RptRow function:

• TM1RptColumn($B$9,”crecords_end:Month”,”All Months”,,””,0,”{[Month].[Month].[All Months]}”)