Formatting actions on a small selection of text with the contents of a textbox in a VBA user-form

Question

I have a textbox within a userform. I want to be able to select a specific portion of text within this textbox and format it like a rich text- for example, embolden it, add a bullet point etc. I am trying to create a command button to enable formatting of this sort. I am unsure of how to get VBA to embolden the selected portion of text. My code does not work. Thank you

Private Sub CommandButton1_Click()
    selectedtext_1 = TextBox1.SelText
    selectedtext_1.Font.FontStyle = "Bold"
End Sub