[pstricks] psset and absolute lengths

[Richard Hensh]

I'm trying to define my own tick marks. I've successfully created macros
to do the job but I have a problem when I scale (using \psset).

Perhaps it'll be clearer with an example. Is there a way to do something
like this:

\def\xTick(#1,#2){%
    \SpecialCoor
    \psline[linewidth=0.35pt,linecolor=black]
        {-}(!#1 #2\space\ticklength sub)%
            (!#1 #2\space\ticklength add)
    \NormalCoor
    }

 where \ticklength is absolute regardless of \psset (for example,
\ticklength = 0.1 cm).

Thanks
ricky