Executing a command on Checkbox.Checked or Unchecked

<CheckBox Content="CheckBox"
          Command="{Binding YourCommand}"
          CommandParameter="{Binding IsChecked, RelativeSource={RelativeSource Self}}" />

If you use MVVM, you can use event triggers like this:

<CheckBox IsChecked="{Binding ServiceOrderItemTask.IsCompleted, Mode=TwoWay}" Content="{Binding ServiceOption.Name}">

    <i:Interaction.Triggers>
          <i:EventTrigger EventName="Checked">
                 <i:InvokeCommandAction Command="{Binding DataContext.IsCompletedCheckedCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type t:RadGridView}}}" CommandParameter="{Binding}"/>
           </i:EventTrigger>

           <i:EventTrigger EventName="Unchecked">
                 <i:InvokeCommandAction Command="{Binding DataContext.IsCompletedUncheckedCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type t:RadGridView}}}" CommandParameter="{Binding}"/>
           </i:EventTrigger>
    </i:Interaction.Triggers>