typesetting an unusual chord

[Stefaan Himpe]

Hello all,

I'm trying to typeset the following somewhat unusual chord:

<f bes des d>4

As is to be expected, the 'des d' notes give a problem.
I found instructions on how to typeset a situation like this in the manual:

naturalplusflat = \markup { \natural \flat }
\relative c'' {
  \once \override Accidental
    #'stencil = #ly:text-interface::print
  \once \override Accidental #'text = #naturalplusflat
  \once \override Score.AccidentalPlacement #'right-padding = #1.5
  <b bes>
}

But I fail to see how I can apply this to my chord above as the "bes" 
also will be affected.

I'd be grateful for some advice.

Best regards,
Stefaan.