Thanks guys, but...

Let me try and be more clear.

The data is coming from a table where the monetary value is always "just" a value so the output looks like:

Example:

Columns.

Inv/Credit Amount

SI-100 10.00

SI-200 12.75

SI- 300 250.00

SC-100 18.50

Where in the Inv/Credit column the id is prefixed with a "SC" I know that's a credit note so in this report - written in BIRT - for the accounts guys, I need to leave the "SI" values "as is" but have a minus symbol where there is a "SC" so it outputs like this:

Columns.

Inv/Credit Amount

SI-100 10.00

SI-200 12.75

SI- 300 250.00

SC-100 -18.50