reflect the style of a char in wpf`s richtextbox in the state of a togglebutton IsChecked false/true

Question

Hello folks,

my first post and a difficult too. I have found any information on msdn forum or google. So I hope to meet a wpf master here.

1.) I have a ToggleButton and a RichTextBox. 2.) I enter text in the RichTextBox , select Text and press the ToggleButton to make the text bold 3.) I set the caret between the bold formatted text and the ToggleButton schould be checked like in word or wordpad, but that is not the case with wpf.

How can I retrieve the single char before the carets position and ask for the singles char formatted style so I can set the IsChecked property of the ToggleButton to true/false?