Hi LSA,
You can use the NMS to view the ifSpeed and ifHighSpeed MIB objects to monitor the current bandwidth of an interface,
The OIDs of the ifSpeed and ifHighSpeed nodes are 1.3.6.1.2.1.2.2.1.5 and 1.3.6.1.2.1.31.1.1.1.15, respectively.
I hope it helps!