while you cannot use an expression in the filter when comparing a FIELD, you can group the report into brackets, and have them collapsed so that you just open up the ones you wish to see...
In the following group text I created groups for 0 - 5 days, 6 - 10 days, 11 - 25 Days, 26 - 50 Days, 51 - 100 Days and > 100 Days
Code is textmode ==>
textmode=true
group.0.iscollapsed=true
group.0.valueexpression=IF(DIV(SUB({actualDurationMinutes},{plannedDurationMinutes}),480)<5,"0 - 5 Days",IF(DIV(SUB({actualDurationMinutes},{plannedDurationMinutes}),480)<10,"6 - 10 Days",IF(DIV(SUB({actualDurationMinutes},{plannedDurationMinutes}),480)<25, "11 - 25 Days",IF(DIV(SUB({actualDurationMinutes},{plannedDurationMinutes}),480)<50,"26 - 50 Days", IF(DIV(SUB({actualDurationMinutes},{plannedDurationMinutes}),480)<100,"51 - 100 Days","Over 100 Days")))))
group.0.valueformat=HTML
group.0.linkedname=direct
group.0.name=Duration Timeframe