How about we identify the fields in a different way and use the Character style that makes it italic.
Code:
Sub SetFieldFormat()
Dim aFld As Field, sCode As String
For Each aFld In ActiveDocument.Fields
sCode = LCase(aFld.Code)
If sCode Like "* ref *" Then
Debug.Print sCode
If aFld.Result.Words.First.Previous = "(" Then
Debug.Print aFld.Result.Words.First.Previous
If sCode Like "*mergeformat*" Then
sCode = Replace(sCode, "mergefield", "charfield")
ElseIf Not sCode Like "*charformat*" Then
sCode = sCode & " \* charformat "
aFld.Code.Text = sCode
End If
aFld.Result.Style = "Emphasis"
aFld.Update
End If
End If
Next aFld
End Sub