IBM has announced a fully documented and supported Prompt API with Cognos 10.2 allowing report authors to now safely use the supported JavaScript API in their reports to control prompts.
From the IBM website:
•The prompt API enables report authors to write JavaScript applications to customize the standard prompt functionality available in IBM Cognos Report Studio to query and set user selections, validate typed-in values using patterns, and set default values using expressions or query data for faster report authoring and a better report viewing experience.
Here's the link to the article:
http://www-01.ibm.com/common/ssi/cgi-bin/ssialias?infotype=AN&subtype=CA&htmlfid=897/ENUS212-282&appname=USN#toc
From the IBM website:
•The prompt API enables report authors to write JavaScript applications to customize the standard prompt functionality available in IBM Cognos Report Studio to query and set user selections, validate typed-in values using patterns, and set default values using expressions or query data for faster report authoring and a better report viewing experience.
Here's the link to the article:
http://www-01.ibm.com/common/ssi/cgi-bin/ssialias?infotype=AN&subtype=CA&htmlfid=897/ENUS212-282&appname=USN#toc