Sub SortEmailsInCell()
    Dim cell As Range
    Dim emails As Variant
    Dim sortedEmails As String
    Dim i As Long, j As Long
    Dim temp As String

        For Each cell In Selection
        If cell.Value <> "" Then
                emails = Split(cell.Value, ",")

                For i = LBound(emails) To UBound(emails) - 1
                For j = i + 1 To UBound(emails)
                    If emails(i) > emails(j) Then
                        temp = emails(i)
                        emails(i) = emails(j)
                        emails(j) = temp
                    End If
                Next j
            Next i

                sortedEmails = Join(emails, ",")

                cell.Value = sortedEmails
        End If
    Next cell
End Sub