wpf checkbox custom attribute binding

I am working with WPF application. In which I have a scenario where I have to bind one custom attribute to checkbox. Please check the below code-

<comboBox.ItemTemplate>
   <DataTemplate>
      <checkbox Name="itemCheck" Content = 
         "{Binding Product}">
         cal:Message.Attach ="[Event 
         Checked] = [Action GetProduct()]"
    </checkbox>
  </DataTemplate>
</comboBox.ItemTemplate>

As per the above code I wanted to bind one more attribute with checkbox that will be in use at time of calling "GetProduct" function.

I tried to bind that with "Content" attribute of checkbox but I need another attribute or custom attribute by which I can bind some other property, because Context attribute is in use for showing Headers.

Can we add custom attribute in checkbox or is there any in-build attribute by which I can bind some property?