How can I draw a line in a canvas that starts at a specific coordinate, but ends dynamically. The line basically needs to start at a point in the canvas and just be a horizontal line that stretches in length with the dynamic length of the grid cell the canvas is located in?

Here's some code:
Code:
<Canvas Grid.Row="1">
  <Line
    X1="10" Y1="8"
    X2="220" Y2="8"
    Stroke="#FFDED0D0"
    StrokeThickness="2" />
</Canvas>
<Canvas Grid.Column="1" Grid.Row="1">
**the line with the dynamic length stretches along this canvas**
</Canvas>
<Canvas Grid.Column="2" Grid.Row="1">
  <Line
    X1="0" Y1="8"
    X2="240" Y2="8"
    Stroke="#FFDED0D0"
    StrokeThickness="2" />
</Canvas>
Thanks for your help!