set TextBox value programatically

[Saima Gul]

Hi
I want to set value in textbox placed in report header section
i see following threads to do it
http://www.telerik.com/community/forums/reporting/telerik-reporting/assign-value-programmatically-to-textbox-in-page-header.aspx
http://www.telerik.com/community/forums/reporting/telerik-reporting/how-to-change-the-content-of-a-textbox-programmatically.aspx
Here is my code

rptAccLedgerReport myReport = new rptAccLedgerReport();

myReport.prm1.Value = "A/c:" +vAccName;

myReport.prm2.Value = "From: " + vFromDate + " To: " + vToDate;

rptAccLedger rptSource = new rptAccLedger();

myReport.DataSource = rptSource.dataSource(vAccNo,vFromDate,vToDate);

rptViewer.Report = myReport; //Set report to reportviewer control

//Here prm1 is text box name and i make it public
When i debug it value is set in text box but when report is rendered value is not displayed 
i also try this

Telerik.Reporting.Report report = (Telerik.Reporting.Report)rptViewer.Report;

Telerik.Reporting.TextBox txt = report.Items.Find("prm1", true)[0] as Telerik.Reporting.TextBox;

txt.Value = "A/c:" + vAccName;

but it does not work
Please help me what is my mistake?