Making specific Text Boldefaced in a TextBox

Question

Hi I currently have a texbox that prints out info to the user when they press diffrent buttons. I was wondering if there was a way to make only some of my text bolded while the rest isnt.

Ive tried the following:

textBox1.FontWeight = FontWeights.UltraBold;
textBox1.Text. = ("Your Name: " );
TextBox1.FontWeight = FontWeights.Regular;
textBox1.Text += (nameVar);

Only problem is that using this way will either make everything bold or nothing. Is there a way to do this? Im using WPF project in C#

Any Comments or suggestions are appreciated. Thanks!

EDIT: So now im trying to do the RichText box that you all suggested but I cant seem to get anything to appear in it:

// Create a simple FlowDocument to serve as the content input for the construtor.
FlowDocument flowDoc = new FlowDocument(new Paragraph(new Run("Simple FlowDocument")));
// After this constructor is called, the new RichTextBox rtb will contain flowDoc.
RichTextBox rtb = new RichTextBox(flowDoc);

rtb is the name of my richtextbox i created in my wpf

Thanks