I think OOTB activity:@baseclass.MSOParseExcelFile is useful for your requirement. It has a Java step where the whole logic is written in it. Basically this activity is used while importing the Requirements/Usecases using AP wizard in V62 and I hope the same is used in V7 too. Study this activity and the way of calling from the referencing rules. You will get an idea on how to achieve your requirement.