Sage 50 Intelligence Reporting Create SUM expression using GROUP BY or PARTITION

I created a Sage 50 Intelligence report and need to create a SUM expression that uses the GROUP BY or PARTITION to be able to create a SUM based on the data in another column. I also want the sum to be included on every row of the data. Does anyone have an example of this type of expression? I can provide more information if this question is not detailed enough.