how to Override Excel File in IIS [Resolved]

hi to all......

Here I done My Application in Mvc3.Functionality is Export data into Excel file.Here I used Stream Writer;This code i used for write the data On Excel file.In My Local System it is working fine i can store the data and i can overrite Previous Data Also.
TextWriter sw = new StreamWriter(fileName);
sw.WriteLine("TestCase ID\tKeyWord Name\tKeyWord Description\tParameter Name\tParameter Description\tParameter Value");
sw.WriteLine(
);
foreach (var item in result)
{ sw.Write(item.TestCaseId + "\t");
sw.Write(item.KeywordName + "\t");
sw.Write(item.Description + "\t");
sw.Write(item.ParamName + "\t");
sw.Write(item.ParamDescription + "\t");
sw.Write(item.ParamValue + "\n");
}
sw.Close();
return View();

but When i Launched In IIS ...It is Not throwing any Error..and i given all permission with the Help of Administrator.But My Excel is not Overite the data.It is showing Previous Data Only.How can i give Virtual file to store in IIS ..Please Guide me...

Thanks in Advance

ManoRama [Resolved]