Remove Image in excel header after exporting the gridview

See more:

VB

ASP.NET

Kindly help me on how to remove image in my excel header. I generate the excel using export command using gridview as source data. Here is my code

Response.AddHeader("content-disposition", "attachment;filename=" & strFilename & ".xls")         
Response.Clear()         
Response.Charset = ""         
Response.ContentType = "application/vnd.xls"           
Dim sw As System.IO.StringWriter = New System.IO.StringWriter()         
Dim htw As System.Web.UI.HtmlTextWriter = New System.Web.UI.HtmlTextWriter(sw)           
grvData.AllowPaging = False         
grvData.AllowSorting = False         
PopulateGrid()          
grvData.RenderControl(htw)         
Response.Write(sw.ToString)         
Response.End() 

Everything was set - except that one my header had a blank header name because of the image that was now shown - the image is came from gridview (I'm using arrow for asc and desc)