filter from find-dired

[<r_mercado@o2.co.uk>]

Hello

I created a helper interactive function for my work that searches 
files from the current
directory that match the name "*subst*".

(defun find-substitutions ()
   "find substitution files in the current directory"
   (interactive)
   (find-name-dired (get-directory-name) "*substitutions*")
   )

I would like to filter the entries that sit under a .svn directory

How would I go about it?

In "plain" find, I found this works

find . -name .svn -prune -o -name "*subst*" -print 

find-dired with the same parameters does not filter the entries under
.svn, instead it includes all .svn directories

Thanks