How to create negative Corner Radius - wpf

Question

So i have this Progress-Bar and on its right side simple Border that inside this Border i want to put Label (The Progress-Baris on the left side):
And here after this 2 Progress-Bar is with value of 100%:
As you can see i can see the Progress-Bar Corner Radius and i want my Border left side will be with negative Corner Radius
My Progress-Bar style:
<Style x:Key="{x:Type ProgressBar}" TargetType="{x:Type ProgressBar}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ProgressBar}">
<Grid MinHeight="14" MinWidth="200">
<Border Name="PART_Track"
CornerRadius="5,0,0,5"
Background="{DynamicResource ProgressBarBackgroundColor}"
BorderBrush="{DynamicResource ProgressBarBackgroundColor}"
BorderThickness="0" />
<Border Name="PART_Indicator"
CornerRadius="8"
Background="{DynamicResource ProgressBarFillBackgroundColor}"
BorderBrush="{DynamicResource ProgressBarFillBackgroundColor}"
BorderThickness="0"
HorizontalAlignment="Left" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
XAML
<StackPanel Orientation="Horizontal">
<ProgressBar Name="progressBar"
Height="20"
Width="700"
Minimum="0"
VerticalAlignment="Center"
Maximum="100"
HorizontalAlignment="Left"
Value="{Binding Progress, UpdateSourceTrigger=PropertyChanged}"
Style="{StaticResource {x:Type ProgressBar}}"
Margin="0,0,0,0"/>
<Border Width="40"
Height="19"
VerticalAlignment="Center"
HorizontalAlignment="Left"
CornerRadius="0,5,5,0"
Margin="0,0,0,0">
<Border.Background>
<SolidColorBrush Color="#FF343D46" Opacity="0.4"/>
</Border.Background>
</Border>
</StackPanel>
**UPDATE**

Answer 1

In essence what you want to do is when you have a progress bar value of 100 you want to apply a different template too the one you have when you are just displaying the progress bar. Use the following XAML:
You can see that in the trigger template - the corner radius property has been set too zero for the correct corners of the progress bar track.
<Style x:Key="{x:Type ProgressBar}" TargetType="{x:Type ProgressBar}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ProgressBar}">
<Grid MinHeight="14" MinWidth="200">
<Border Name="PART_Track"
CornerRadius="5,0,0,5"
Background="{DynamicResource ProgressBarBackgroundColor}"
BorderBrush="{DynamicResource ProgressBarBackgroundColor}"
BorderThickness="0" />
<Border Name="PART_Indicator"
CornerRadius="5"
Background="{DynamicResource ProgressBarFillBackgroundColor}"
BorderBrush="{DynamicResource ProgressBarFillBackgroundColor}"
BorderThickness="0"
HorizontalAlignment="Left" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="Value" Value="100">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ProgressBar}">
<Grid MinHeight="14" MinWidth="200">
<Border Name="PART_Track"
CornerRadius="5,0,0,5"
Background="{DynamicResource ProgressBarBackgroundColor}"
BorderBrush="{DynamicResource ProgressBarBackgroundColor}"
BorderThickness="0" />
<Border Name="PART_Indicator"
CornerRadius="5,0,0,5"
Background="{DynamicResource ProgressBarFillBackgroundColor}"
BorderBrush="{DynamicResource ProgressBarFillBackgroundColor}"
BorderThickness="0"
HorizontalAlignment="Left" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Trigger>
</Style.Triggers>
This will result in the following behaviour: