Crystal Reports Group results in a different group

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Hello, 
I`ve got a report where I want to group results by a deal number but also want to sum one field by another group. 

I have my fields in group footer which is grouped by deal_no. 

Then I have a field where I`m trying to summarize amount per a column comments in DB using command: 
Sum({Command.AMOUNT},{Command.TRIM(REGEXP_REPLACE(B.COMMENTS,'CUM'))})
So I`ve got another group in my report - {Command.TRIM(REGEXP_REPLACE(B.COMMENTS,'CUM'))}. 

Since I want to have my report sorted by deal_no I`ve got them in group footer grouped by DEAL_NO. However, if I count the sum of the field above it also summarize the results by deal number but I`d like to have it summarized by the command. 

Is there any way how to do it? Can I summarize a field grouped by command within another group (grouped by deal_no)?

Thank you.

Best regards,

Petr