iam using this code to change the font in a richtextbox it's work if user select a single font if there are multiple fonts, and font sizes it dosenot work, any help please

Code:
If ToolStripComboBox2.Items.Contains(ToolStripComboBox2.Text) Then
RichTextBox1.SelectionFont = New Font(ToolStripComboBox2.Text, RichTextBox1.SelectionFont.Size, RichTextBox1.SelectionFont.Style)
End If