How to replace xml file with a variable in Data Model in pentaho analysis viewer ?

Hi,

I want to dynamically create xml content which can be used for the MDX query in Pentaho Analysis Viewer in design studio.
For that I have used Javascript component and passed the xml file content in a variable.
Next in the Pentaho Analysis Viewer I have selected this variable in the Data Model, but while executing the xaction I got the below error:
'An error occurred while rendering Pivot.jsp. Please see the log for details.'

Please tell if I have done something wrong or is there any other possible way.

Thanks