vertical arrow

[Orm Finnendahl]

Hi,

I'm trying to produce a vertical arrow with arbitrary length at a
specified horizontal position above the staff, preferrably with a
definable dashed line. I got the arrowhead with the following markup
command but don't get the line of the arrow:

^\markup{\arrow-head #1 #-1 ##t}

Is that somewhere documented? I know that I can get it done with
inline postscript but I'm looking for a generic solution in lilypond.

--
Orm