How To Change Fileupload Name

im using following code to upload

protected void UploadButton_Click(object sender, EventArgs e)
{
if(FileUploadControl.HasFile)
{
try
{
string filename = Path.GetFileName(FileUploadControl.FileName);
FileUploadControl.SaveAs(Server.MapPath("~upload/") + filename);
StatusLabel.Text = "Upload status: File uploaded!";
}
catch(Exception ex)
{
StatusLabel.Text = "Upload status: The file could not be uploaded. The following error occured: " + ex.Message;
}
}
}

i want to cahnge upload file name...i have to assign file name for every uploaded file how?