How to pass variable's value from subreport to main report and show/hide detail band on the basis of that value?

Hi,

 I am storing Value of one field in a variable in subreport. This variable I am returning to Main report. On the basis of this value I want to show/hide detail band 2. But I am not able to implement this as the value returned by the subreport is always Null which is a shock to me as when I am displaying the same value in subreport itself it is giving me 2 (integer).  Please help me out with this.