How to have Counter Kind of variable in Reporting services 2008

Hi,
In My report i have 10 SubReports, and each subreport is made visible according to the condition. Now i want to give the Numbering for the each subreport. So is there is any global variable kind of thing where i can increment the Variable on visibility of the each subreport and assign the value to the subreport.
   I hope so my question is understandable, sorry for bad English.

Thanks in Advance
Naren