I have found a way to do so.
1. Select the Rich Text Content Control
2. Properties (Developer Tab - Controls)
3. Use a style to format contents
However, how could I do this in VBA?
Code:
Sub a()
Dim oStyle As Style
Set oStyle = ActiveDocument.Styles.Add("Style1", wdStyleTypeParagraph)
Dim oControl As ContentControl
With oStyle
.QuickStyle = True
.Font.Underline = wdUnderlineThick
.Font.UnderlineColor = wdColorBlack
.Font.Italic = True
.Font.ColorIndex = wdRed
End With
For Each oControl In ActiveDocument.ContentControls
'''
''' ???
'''
Next oControl
End Sub