Increase font size of text based on slider - wpf

Question

So my requirement is quite simple. I will have a slider control and a textblock. So whenever the slider is increased or decreased the font size of the Textblock should change. I am able to accomplish this quite simple using MVVM pattern.
My problem is I need to show some text below the slider like small, medium, low. Well I was able to read some articles online that says this can be accomplished using a TickBar. But problem is there is no value changed event with TickBar so that I can trigger changes to the ViewModel.
Can someone give me an idea of accomplishing this using slider. I have read some style on google and heres what it does it displays numbers as soon as the slider changed. Can it be changed to text like small, medium, low. Thanks.
<Style
x:Key="SliderRepeatButton"
TargetType="RepeatButton">
<Setter
Property="SnapsToDevicePixels"
Value="true" />
<Setter
Property="OverridesDefaultStyle"
Value="true" />
<Setter
Property="IsTabStop"
Value="false" />
<Setter
Property="Focusable"
Value="false" />
<Setter
Property="Template">
<Setter.Value>
<ControlTemplate
TargetType="RepeatButton">
<Border
Background="Transparent" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style
x:Key="SliderRepeatButton1"
TargetType="RepeatButton">
<Setter
Property="SnapsToDevicePixels"
Value="true" />
<Setter
Property="OverridesDefaultStyle"
Value="true" />
<Setter
Property="Template">
<Setter.Value>
<ControlTemplate
TargetType="RepeatButton">
<Border
SnapsToDevicePixels="True"
Background="YellowGreen"
BorderThickness="1"
BorderBrush="YellowGreen"
Height="3" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style
x:Key="SliderThumb"
TargetType="Thumb">
<Setter
Property="SnapsToDevicePixels"
Value="true" />
<Setter
Property="OverridesDefaultStyle"
Value="true" />
<Setter
Property="Template">
<Setter.Value>
<ControlTemplate
TargetType="Thumb">
<StackPanel
Orientation="Vertical">
<Path
Data="M 0 0 L 8 0 L 4 6 Z"
Stroke="YellowGreen"
Margin="-2,0,0,0"
StrokeThickness="2"
Fill="YellowGreen"></Path>
<Line
X1="0"
Y1="0"
X2="0"
Y2="7"
Stroke="Gray"
StrokeThickness="1"
Margin="2,0,0,0"
StrokeDashArray="1.5,1.5"></Line>
<TextBlock
Foreground="Black"
Margin="-2,30,0,0"
Text="{Binding Value, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Slider}}}" />
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<ControlTemplate
x:Key="Slider"
TargetType="Slider">
<Grid>
<Grid.RowDefinitions>
<RowDefinition
Height="Auto" />
<RowDefinition
Height="Auto"
MinHeight="{TemplateBinding MinHeight}" />
<RowDefinition
Height="Auto" />
</Grid.RowDefinitions>
<TickBar
x:Name="TopTick"
Fill="LightGray"
VerticalAlignment="Top"
SnapsToDevicePixels="True"
Grid.Row="0"
Placement="Top"
Height="5"
Visibility="Visible" />
<Border
BorderBrush="LightGray"
BorderThickness="0,0,0,1"></Border>
<Border
x:Name="TrackBackground"
VerticalAlignment="Center"
Margin="0,-10,0,0"
BorderBrush="Red"
Background="Red"
Height="3"
Grid.Row="1"
BorderThickness="1" />
<Track
Grid.Row="1"
x:Name="PART_Track"
Margin="0,-10,0,0">
<Track.DecreaseRepeatButton>
<RepeatButton
Style="{StaticResource SliderRepeatButton1}"
Command="Slider.DecreaseLarge" />
</Track.DecreaseRepeatButton>
<Track.Thumb>
<Thumb
Style="{StaticResource SliderThumb}"
Margin="0,-20,0,0" />
</Track.Thumb>
<Track.IncreaseRepeatButton>
<RepeatButton
Style="{StaticResource SliderRepeatButton}"
Command="Slider.IncreaseLarge" />
</Track.IncreaseRepeatButton>
</Track>
<TextBlock
Text="0"
Grid.Row="1"
Margin="0,15,0,0"></TextBlock>
<TickBar
x:Name="BottomTick"
Fill="LightGray"
SnapsToDevicePixels="True"
Grid.Row="2"
Placement="Bottom"
Height="4"
Visibility="Collapsed" />
</Grid>
<ControlTemplate.Triggers>
<Trigger
Property="TickPlacement"
Value="TopLeft">
<Setter
TargetName="TopTick"
Property="Visibility"
Value="Visible" />
</Trigger>
<Trigger
Property="TickPlacement"
Value="BottomRight">
<Setter
TargetName="BottomTick"
Property="Visibility"
Value="Visible" />
</Trigger>
<Trigger
Property="TickPlacement"
Value="Both">
<Setter
TargetName="TopTick"
Property="Visibility"
Value="Visible" />
<Setter
TargetName="BottomTick"
Property="Visibility"
Value="Visible" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
<Style
x:Key="Horizontal_Slider"
TargetType="Slider">
<Setter
Property="Focusable"
Value="False" />
<Setter
Property="SnapsToDevicePixels"
Value="true" />
<Setter
Property="OverridesDefaultStyle"
Value="true" />
<Style.Triggers>
<Trigger
Property="Orientation"
Value="Horizontal">
<Setter
Property="MinHeight"
Value="21" />
<Setter
Property="MinWidth"
Value="104" />
<Setter
Property="Template"
Value="{StaticResource Slider}" />
</Trigger>
</Style.Triggers>
</Style>