Pass value from main report to sub report

I am designing a report which includes sub report every thing is fine but i have to display the main report field value in sub report . To get the main report vale in to the sub report follow the bellow steps.
Step 1:
1. In main report create a formula, name it, edit it with the formula editor as follows:
Shared numbervar NAME := {Rep.Sno} 
Save formula.  Note that you should replace the name and type of variable and a formula with ones of your own
2. Now create a formula in your subreport, name it, edit it with the formula editor as follows:

Shared numbervar NAME;
NAME

3. Use formula created in step 2 in your report (drag drop in the report from formula fields.
Note that subreport is processed after the main report, so it's easier to pass values from main report to subreport.