Automatic refresh of pivot table on changes in external data source.

Hi,
I have a pivot table report connected to an external data source (OLAP cube).I want to automatically refresh the pivot table report everytime the OLAP cube data changes.

I know we can use Automatic refresh on open of workbook or time intervals after which to refresh .But i want the auto refresh to work even if the workbook is already open and there is no definite time interval after which the cube is likely to change.SO,by defining intervals for auto refresh i do not intend to waste time refreshing even if there is no change.

There are multiple pivot table reports and pivot charts connected to the same OLAP cube.

Is it possible through some macros and if so can anyone share the same.I have no knowledge of writing macros for Excel.

Thanks.