WEB-I Formula issue

Hi All,

Facing issue with WEB-I formula:

my formula is like :

April attrition = (April 2012 attrition/(March 2012 head count + April 2012 head count))

but in my variable screen I am passing fiscal year 2013.

so value will pick from April 2012 to march 2013.

so how can i pick 2012 March and how can i pass this value in to formula.

Please suggest me.

Thanks & Regards,

Samar