Why Same Data EveryTime???? Please Help

Hello Friends,

i am having a problem while using Crystal Report. 

i have created one Report.aspx page. When it loads, it display a text box where user enter receipt number and  click show button. the receipt is generated successfully.

The problem arises every time when user without unloading the page, enter new receipt number. The report show the same receipt for all other receipt numbers. The code is as follows

ReportDocument doc = new ReportDocument();

doc.Load(Server.MapPath("~/Reports/rptReceipt.rpt"));

doc.SetParameterValue(0, tReceiptNo.Text);

crvReceipt.ReportSource = doc;

crvReceipt.RefershReport();