Hiding columns upon download from gridview to excel

[hedgracer]

I have a gridview that has six columns. I need to hide the last column
(i.e. not download it) in the download from gridview to excel. My
current code (which downloads the entire gridview) is as follows:

public static void ExportExcelFile (Control htmlData, string
filename)
{
HttpContext.Cur rent.Response.C lear();
HttpContext.Cur rent.Response.A ddHeader("conte nt-disposition",
"attachment;fil ename="
+ filename + ".xls");
HttpContext.Cur rent.Response.C harset = "";
HttpContext.Cur rent.Response.C ontentType = "applicatio n/
vnd.xls";
System.IO.Strin gWriter stringWrite = new
System.IO.Strin gWriter();
System.Web.UI.H tmlTextWriter htmlWrite = new
HtmlTextWriter( stringWrite);
htmlData.Render Control(htmlWri te);
HttpContext.Cur rent.Response.W rite(stringWrit e.ToString());
HttpContext.Cur rent.Response.E nd();
}

I am calling this by the following code:

protected void btnDownloadDebi t_Click(object sender, EventArgs e)
{
grvDebit.Column s[5].Visible = false;
Util.ExportExce lFile(grvDebit, "DebitDetai l");
grvDebit.Column s[5].Visible = true;

}

I thought that making the fifth column's visible property to false
before the call would result in that column not being downloaded. I
was wrong. Can anyone give me some advice on this? Thanks for all help
in advance.

Dave