Make string bold

Hello,

Can someone please tell me how to make part of a sentence bold in vba? Here is what I have so far:

Private Sub CommandButton1_Click()
Dim bold As String

bold = "SAVE"

    Range("C1:E24").Select
    ActiveWorkbook.EnvelopeVisible = True
    With ActiveSheet.MailEnvelope
      .Introduction = "Do not forget to click " & bold
      .Item.To = "Me"
      .Item.Subject = "Random Process Review Schedule"
      .Item.Display
   End With
End Sub

I would like to make the word "SAVE" bold.

thank you,