<StackPanel xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Background="Gray" Orientation="Vertical" VerticalAlignment="Center">

<Slider x:Name="PART_Slider" Orientation="Horizontal" Height="22" Maximum="100" Value="4" Width="300"/>

    <ProgressBar Height="29.532"  Value="{Binding Value, ElementName=PART_Slider}" Width="300">

        <ProgressBar.Style>
            <Style TargetType="{x:Type ProgressBar}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate>

                            <Grid>
                                <Rectangle x:Name="PART_Indicator" Fill="Pink" HorizontalAlignment="Left"/>
                                <Border x:Name="PART_Track" Background="Black"/>
                                <Grid>
                                    <Grid.OpacityMask>
                                        <VisualBrush Visual="{Binding ElementName=PART_Indicator}"/>
                                    </Grid.OpacityMask>
                                    <Rectangle Fill="White"/>
                                </Grid>
                            </Grid>

                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </ProgressBar.Style>

    </ProgressBar>

</StackPanel>