The dude traffic notification

Hi!

I need to monitor the traffic into a interface who receives internet link.
This monitoring must send one SMS if the traffic is below than a specific band. (for example 10mbps)
Alright, the send of SMS is running correctly with other notifications who i have.
But i need to know how i can monitor a single interface with SNMP and send a SMS if the traffic is to low?
I searched about this, but i don’t found anything related with this.
The only think that i found is monitor the SNMP using the oid.

Please, can anyone help me?
Thanks everyone!

http://forum.mikrotik.com/t/norification-if-speed-on-a-link-drops/39246/1

Hi.
I just see this topic and this was very usefull.
This solved my problem.
Thanks.