not possible within a formula, ok with text only
just make sure you remove formula and keep value by paste special function
Sub test()
With ActiveCell
s = Application.Evaluate(.Formula)
.NumberFormat = "@"
.Value = s
.Characters(Start:=1, Length:=2).Font.FontStyle = "bold"
End With
End Sub
Private Sub Worksheet_Change(ByVal Target As Range)
Dim Rg As Range, L&
Application.EnableEvents = False
For Each Rg In Intersect(Target, [A1:C5]).Rows
L = Cells(Rg.Row, 2).Value > ""
With Cells(Rg.Row, 3)
.Font.Bold = False
.Value = IIf(L, "'", "") & Cells(Rg.Row, 1).Value & IIf(L, "/" & Cells(Rg.Row, 2).Text, "")
L = Len(Cells(Rg.Row, 1).Text)
If L Then .Characters(1, L).Font.Bold = True
End With
Next
Application.EnableEvents = True
End Sub