I just learned that you can use format names in a Format function -- my Excel lesson for the day, thanks, Roy.

You could generalize Roy's approach a tad:
Private Sub TextBox1_Exit(ByVal Cancel As MSForms.ReturnBoolean)
    FormatCurrency Me.TextBox1
End Sub

Private Sub TextBox2_Exit(ByVal Cancel As MSForms.ReturnBoolean)
    FormatCurrency Me.TextBox2
End Sub

Sub FormatCurrency(ctl As MSForms.TextBox)
    If Len(ctl.Value) Then ctl.Value = Format(ctl.Value, "Currency")
End Sub