Eh no worries, everyone's bound to be new at something at some point. Anyhow like I said in the comment. The ToggleButton doesn't have the functionality you're looking for by default. Switching to a RadioButton
and just styling it to look like your button would make life easier moving forward to provide the behavior you're after.
You can find information and default templates in the MSN docs and using Blend makes editing templates fairly easy, for your instance you could just plop a RadioButton
on the designer, right-click it, and choose "edit template -> edit a copy" to add a copy of the control template to your view to edit to your hearts content.
Hope this helps, and if you run into anything along the way come on back and we'll get you sorted. Cheers