I have an ASP.NET page which has report viewer control to access reports from report manager.
Thanks.
I'm assuming your using remote processing of the report.
Then do the following:
ReportParameter p = new ReportParameter("ParamName", "ParamVal");
reportViewer1.ServerReport.SetParameters(new ReportParameter[] { p });
From: http://msdn.microsoft.com/en-us/library/ms252178(VS.80).aspx
Good example: http://www.codeproject.com/KB/reporting-services/ReportViewer2005.aspx