<asp:TemplateField >
                     <ItemTemplate>
                         <asp:ImageButton ID="ImgButWarning" runat="server" CausesValidation="false" ShowHeader="False"
                             CommandName="" ImageUrl="~/Img/102.png" Text="Button" />
                     </ItemTemplate>
                 </asp:TemplateField>

protected void GridView3_RowDataBound(object sender, GridViewRowEventArgs e)
        {
         

            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                
                if ((e.Row.Cells[10].Text == "2") & (Convert.ToDateTime(e.Row.Cells[11].Text)) <= DateTime.Now.AddMonths(-3)) 
                   

                {
                    e.Row.BackColor = System.Drawing.Color.Pink;
               

                   ButtonField btn = (ButtonField)e.Row.FindControl("ImgButWarning");
                   //здесь вставить надо что то вроде      ((ImageButton)gvRow.Controls[0].Controls[0]).ImageUrl = "~/Img/warning.png";                 

                   

                                }

                e.Row.Cells[10].Visible = false;
                GridView3.HeaderRow.Cells[10].Visible = false;
                e.Row.Cells[11].Visible = false;
                GridView3.HeaderRow.Cells[11].Visible = false;

            }
        }