WPF

<StackPanel>
    <ComboBox Margin="5" x:Name="myComboBoxThickness" >
        <ComboBoxItem Content="Thick" />
        <ComboBoxItem Content="Thin" />
        <ComboBoxItem Content="Thinner" />
        <ComboBoxItem Content="None" />
    </ComboBox>
    <Border x:Name="ThisBorder" >
        <Border.Style>
            <Style>
                <Style.Triggers>
                    <DataTrigger Binding="{Binding ElementName=myComboBoxThickness, Path=SelectedItem.Content}" Value="Thick">
                        <Setter Property="Border.BorderThickness" Value="10"/>
                        <Setter Property="Border.BorderBrush" Value="Aqua"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding ElementName=myComboBoxThickness, Path=SelectedItem.Content}" Value="Thin">
                        <Setter Property="Border.BorderThickness" Value="5"/>
                        <Setter Property="Border.BorderBrush" Value="Green"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding ElementName=myComboBoxThickness, Path=SelectedItem.Content}" Value="Thinner">
                        <Setter Property="Border.BorderThickness" Value="2"/>
                        <Setter Property="Border.BorderBrush" Value="Yellow"/>
                    </DataTrigger>
                    <DataTrigger Binding="{Binding ElementName=myComboBoxThickness, Path=SelectedItem.Content}" Value="None">
                        <Setter Property="Border.BorderThickness" Value="0"/>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </Border.Style>
        <TextBlock Text="This is a test arena!!!!!!!!!!!!" />

    </Border>
</StackPanel>

public enum BorderTypes
{
    // Summary:
    //     Display the border as thick.
    Thick = 0,
    //
    // Summary:
    //     Display the border as thin.
    Thin = 1,
    //
    // Summary:
    //     Display the border as thinner.
    Thinner = 2,
    //
    // Summary:
    //     Do not display the border.
    None= 3,
}

#region BorderThicknessProperty DP

/// <summary>
/// Bound Data Dependency Property
/// </summary>
public static readonly DependencyProperty myBorderThicknessProperty =
    DependencyProperty.Register("myBorderThickness", typeof(BorderTypes), typeof(TestControl),
        new FrameworkPropertyMetadata(BorderTypes.Thick, new PropertyChangedCallback(OnBorderThicknessPropertyChanged)));

/// <summary>
/// Gets or sets the Bound Data property.
/// </summary>
public BorderTypes myBorderThickness
{
    get { return (BorderTypes)GetValue(myBorderThicknessProperty); }
    set { SetValue(myBorderThicknessProperty, value); }
}

/// <summary>
/// Handles changes to the ToolbarVisibility property.
/// </summary>
private static void OnBorderThicknessPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    BorderTypes ds = (BorderTypes)e.NewValue;
    //Use a switch to set the thickness
    switch (ds)
    {
        case BorderTypes.Thick :
            {
                ((TestControl)d).<Name of your control here to set the border thickness on>.BorderThickness = 10;
            }
            break;
    }
}

#endregion