I am writing a script which will add a new project in the repository, based on the name supplied by the user. Part of this involves checking that an url with the same name does
You can just use
svn ls https://developernetwork.repo.net/svn/Projects/Calculator/
It will tell you if the repository(directory) exist or not.
Update
for directories with many files use:
svn ls http://server/svn/foo --depth empty