I have 2 sub reports in one main report. Each sub report has its own sub total, however I wish to add the total of these 2 sub reports and show it at the main report.
Having the need to extract data from detail report into main report means that your design/architecture is not correct. You should have that data in main report if you need to show it as part of the main report. And as with all things that are not natively supported, you can accomplish your task with the help of report events: