I HAVE TAX COLUMN AND AT THE BOTTOM I WANT TO HAVE THE SUM OF ALL ROWS. IN MY CASE I WANT TO EXCLUDE ONE PRODUCT FROM IT BELOW IS THE RESULT THAT IS NEED ('C' IS EXCLUDED)
| ROW | TAX |
| ----| -----|
| A | 20 |
| B | 30 |
| C | 10 |
|SUM | 50 |
An IIF can be used inside the aggregate function to replace the value of TAX with zero if ROW is C.
=SUM(IIF(Fields!ROW.Value = "C", 0, Fields!TAX.Value))
If the TAX field is not an INTEGER, then you may need to wrap the 0 in a CDEC function to convert it to decimal.
=SUM(IIF(Fields!ROW.Value = "C", CDEC(0), Fields!TAX.Value))