Crystal Reports Selection Criteria for a single forumla

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     Hey guys, 

I'm new to crystal reports, and I have a quick question...

I'm creating a report that has the following set up

                           Residential              Commercial            Industrial

Cooltown             %change1               %change2            %change3  

Notsocooltown              "                             "                            "

coolesttown

all towns

I have the grouping done by the variable town, however, to put in the % change forumla {(2008 - 2005/2008)*100} for each of the headers (residential, commercial, industrial) is there any way to write the formula so that it only includes residential data?

(ie if rtc = 'R' then %change1 = {((2008-2005)/2005)*100}
     if rtc = 'C' then %change2 = {((2008-2005)/2005)*100} etc...)

(I've tried the above and it doesn't work....) I'm sure cross tabs are an option, however I'd like to get this to work if possible (the format of my report is set up differently, so I don't want to use crosstabs if possible)

Thanks a lot for all help