I have a problem with my wpf treeview. It\'s code goes like this:
If I understand your question correctly you want to Stretch the TreeViewItems and align Value to the right. To get the TreeViewItems to Stretch Horizontaly you'll need to edit the Template for TreeViewItem. The problem is explained here: http://leecampbell.blogspot.com/2009/01/horizontal-stretch-on-treeviewitems.html
Here is an edited version of the TreeViewItem which does this. Note that you'll have to add a reference to PresentationFramework.Aero for this to work
Sample
StretchTreeViewItemStyle