Difference between "Network path not found" and "Access denied" in C#

In my C# .NET 2.0 application I'm accessing network paths, and I'd like to be able to tell the difference between paths that don't exist, and paths which do exist but for which I don't have access rights. I tried doing the following:

try
{
    string[] contents = Directory.GetFileSystemEntries( path );
}
catch( Exception e )
{
    if( e is DirectoryNotFoundException )
        MessageBox.Show( "Path not found" );
    else
        MessageBox.Show( "Access denied" );
}

This works fine for local paths, but for network paths, the exception is always System.IO.IOException, regardless of the reason for the error. The exception Message field shows a different message depending on whether the path exists or not, so clearly the information is available at some point, but I can't get to it. Is there a way to differentiate between "path not found" and "access denied" for network paths?

Edit: So, in case anyone else wants the quick solution to this, as suggested by henrik, and incorporating peSHIr's advice, here is what you can do:

try
{
    // Issue this call just to find out whether the path exists
    // We don't care about the result

    string[] contents = Directory.GetFileSystemEntries( path );

    // If we get this far then the path exists.
}
catch( IOException e )
{
    uint error = (uint)Marshal.GetHRForException( e );

    if( error == (uint)0x80070041 )     // ERROR_NETWORK_ACCESS_DENIED
    {
        // The poor deluded user doesn't have access rights

        this.SuperProprietaryTechniqueForGettingAccessRights();
    }
    else
    {
        // Hah! The idiot user specified a path that doesn't exist!
        // Chastise them severely, like all good GUI should.

        MessageBox.Show( "NO! BAD USER!" );
    }
}
catch 
{
    // Swallow all other types of exception - we only made the call
    // to find out whether the path exists.
}

First, I would not catch (Exception), but do something like this:

try {
  string[] contents = Directory.GetFileSystemEntries(path);
}
catch(DirectoryNotFoundException)
{
  MessageBox.Show("Path not found");
}
catch(IOException)
{
  MessageBox.Show("Could not access path");
}

But the real question is: why would you actually need to know the difference, if all you do is show a message box to the user with a generic error message?