I’m not entirely sure why I’m running the wiki searches for you that YOU should be doing.
http://wiki.mikrotik.com/wiki/Dynamic_DNS_Update_Script_for_dynDNS
That also uses a URI to update records. Adapt it accordingly.
Or search Google for “mikrotik no-ip.com”. First hit: http://forum.mikrotik.com/t/dynamic-dns-script-no-ip-and-others/33205/1