TextBox inside GridView's TextChanged event is fire multiple times .

<asp:GridView ID="gridReviewLog" runat="server" AutoGenerateColumns="false" OnRowEditing="gridReviewLog_RowEditing">
        <Columns>
            <asp:TemplateField HeaderText="Employee Name">
                <ItemTemplate>
                    <asp:TextBox ID="txtempname" runat="server" MaxLength="11" Value='<%#DataBinder.Eval(Container.DataItem,"NAME") %>'  Enabled="false"></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Employee Role">
                <ItemTemplate>
                    <asp:TextBox ID="txtrole" runat="server" Value='<%#DataBinder.Eval(Container.DataItem,"ROLE") %>' MaxLength="11"  Enabled="false"></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Actual Minute">
                <ItemTemplate>
                    <asp:TextBox ID="txtactualMin" runat="server"  Value='<%#DataBinder.Eval(Container.DataItem,"ACTUALMINUTES") %>' MaxLength="11"  Enabled="false"></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Revised Minute">
                <ItemTemplate>
                    <asp:TextBox ID="txtrevisedmin" runat="server" AutoPostBack="true" OnTextChanged="txtrevisedmin_TextChanged" MaxLength="11" Value='<%#DataBinder.Eval(Container.DataItem,"REVISEDMINUTES") %>' Enabled="true"></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
            <asp:TemplateField HeaderText="Employee Cost(per hour)">
                <ItemTemplate>
                    <asp:TextBox ID="cost" runat="server" MaxLength="11" Value='<%#DataBinder.Eval(Container.DataItem,"RATE") %>' Enabled="false"></asp:TextBox>
                </ItemTemplate>
            </asp:TemplateField>
        </Columns>
    </asp:GridView>

protected void txtrevisedmin_TextChanged(object sender, EventArgs e)
        {
            List<GridRevise> GVList = (List<GridRevise>)ViewState["GridviewList"];
            TextBox thisTextBox = (TextBox)sender;
            GridViewRow currentRow = (GridViewRow)thisTextBox.Parent.Parent;
            int rowIndex = 0;
            rowIndex = currentRow.RowIndex;
        }