On Windows, you can flush your DNS cache at any time by typing "ipconfig /flushdns" in cmd.exe (or on Linux, type "/etc/rc.d/init.d/nscd restart"). Your computer will then automatically refill your cache with up-to-date entries as you browse the net afterwards, so there won't be any need to mess with your "hosts" file.
Actually, I wouldn't recommend using your hosts file to hardcode IP addresses for anything (if that's what you're doing), since the DNS protocol is practically what the entire internet is based on and local 'hosts' configurations are really only around for local routing/networking purposes. If you set dynasty-scans.com to some specific IP address in your hosts file then you might need to update it again if it is ever updated later.