WPF：向列宽添加5个像素

I have a Grid with 4 columns:

我有一个有4列的网格:

<Grid.ColumnDefinitions>
    <ColumnDefinition Width="14" />
    <ColumnDefinition Width="10" />
    <ColumnDefinition Width="{TemplateBinding ActualWidth}" />
    <ColumnDefinition Width="10" />
</Grid.ColumnDefinitions>
<