How to (quickly) check if UNC Path is available

How can I check if a UNC Path is available? I have the problem that the check takes about half a minute if the share is not available :

var fi = new DirectoryInfo(@"\\hostname\samba-sharename\directory");

if (fi.Exists)
//...

Is there a faster way to check if a folder is available? I'm using Windows XP and C#.