How to make the first value in a value prompt(Radio Button) as default selection

[sreenivas445]

Hi
I have a value prompt (Radio Button) which is created with a level Report Period Year which has members 2011, 2012 and 2013 , I have given it the descending order , so the order is 2013,2012, 2011 . I can give 2013 as default selection as 2013, but the problem is the default selection has to be dynamic for future perspective ie, when the year changes to 2014 , the default selection should be 2014, Please suggest me how to achieve this . I am using Cognos 10.1 version.
FYI ,  the radio button prompt looks horizontal, not vertical, by using HTML script.

Thanks a lot!!!