Now needed something else. placing the value of the negative col2 instead of 0.

I've tried doing the following ways and not resulted, where I am going wrong?

=SUM(IIF(Fields!col3.Value = "DEL",CDec(Fields!col2.Value)-(Fields!col2.Value),CDec(Fields!col2.Value)))

=SUM(IIF(Fields!col3.Value = "DEL",CDec(Fields!col2.Value)*(-1),CDec(Fields!col2.Value)))