is there a way to detect the computer name doesn't exist?

I have an auto-backup when the client exit the program, the client can create the backup file to ______ (eg. c:\mybackup or \\backuppc\mybackup)
however if someone turns off the \\backuppc, program will error
is that away to detect that \\backuppc is not exist hence the program doesn't continue the process?

Thanks in advance

Jerry