Focus changed on LoadMore Button click in Windows Phone Application Page - windows-phone-7

Question

In my Windows Phone application I have a ListBox with Load More button, in one of my pages. At the bottom of the page a TextBox and a button is present. when I click on the Load More button at the bottom of listbox, the focus automatically goes to the textbox and the keypad is shown. I don't need to go the focus to the textbox on buttonclick. How this problem occures and how can I overcome this problem.
The xaml of style used for the listbox shown below
<phone:PhoneApplicationPage.Resources>
<Style x:Key="ListBoxMore" TargetType="ListBox">
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Foreground" Value="{StaticResource PhoneForegroundBrush}"/>
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Disabled"/>
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Visible"/>
<Setter Property="BorderThickness" Value="0"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ListBox">
<ScrollViewer x:Name="ScrollViewer">
<StackPanel>
<ItemsPresenter/>
<Border BorderBrush="Black" BorderThickness="0,0.5">
<Button Content="Load More..." Name="btnLoadMore" Visibility="Visible" Background="White" Foreground="#FF176DDC" Click="btnLoadMore_Click"></Button>
</Border>
</StackPanel>
</ScrollViewer>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</phone:PhoneApplicationPage.Resources>
The xaml of the listbox shown below
<ListBox x:Name="userDetailsList" SelectionMode="Multiple" Style="{StaticResource ListBoxMore}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Border BorderThickness="0,0.5,0,0" BorderBrush="Black" Width="440">
<Grid Width="430">
<Image Source="{Binding UserImage}"/>
<TextBlock Text="{Binding UserName}"/>
<TextBlock Text="{Binding Details}"/>
<TextBlock Text="{Binding Date}"/>
</Grid>
</Border>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
When I click on loadmore button the focus goes to the textbox that placed below the listbox. There is only one textbox is there.