Yes this can be done, but you will need to refer to GetSummary instead of directly referring to the summary field in your conditional format expression.
If your summary field is called sTotal, and your sub summary part is set to be visible, "When sorted by" Type, you'd use this expression to turn Type A items red when the sTotal sub total is < 50
Get Summary ( sTotal ; Type ) < 50
Of course this expression will cause Type B and C items to show red at sub totals < 50. You'd need to put these values in a related table so that you can refer to that field via a relationship instead of the literal value: 50, 45 or 125.
Get Summary ( sTotal ; Type ) < RelatedTable::Field
How do i set the type to each item?
Get Summary (sTotal ; Type ) < RelaedTable: Qty Level
How would it know what type? If type is "balloon" and the qty is less than 50...turn red.
If type is "jacket" and the qty is less than 125...turn red.
I assumed you had a field name "Type" that was the "sorted by" field for you Sub Summary part.
Your related table would link by this same table:
Type: "balloon", "Jacket", etc.
WarningLevel: 50, 12 etc.
A relationship linking the two tables:
ReportLayoutTable::Type = WarningLevels::Type
Then Your conditional fromat expression would be:
Get Summary ( sTotal ; Type ) < WarningLevels::WarningLevel
You may already have a table where you have one record for each "Type" where you can add this warning level field and use a relationship based on Type to it.