If you are building a custom table visualization; you should be able to use the expordData property as a function: http://help.qlik.com/en-US/sense-developer/3.2/Subsystems/APIs/Content/ExtensionAPI/exportdata-property.htm
I am not sure if this is possible for native objects.
I hope this helps,
Did you find any solution for this problem. In our case, when data volume is very high, the table is not loading and its causing CPU and memory to 100% utilization within few seconds. I could find the way to restrict no of records to be viewed using calculation condition but the way we built export functionality, its again trying to export everything irrespective of calculation condition. Looking for better solution to this problem.