SNMP Custom Monitors : available functions

I'm using OpManagerEE, latest service pack and am trying to create a custom monitor for Cisco's WLC devices, specifically the number of rogue access points.
I found the necessary mib (AIRESPACE-WIRELESS-MIB) and its dependencies but the closest information I get is a SNMP table that contains information for each of these APs. Is there any way to return the count of how many elements there are in this table, since I'm interested in this number, not in all the details.

Also, is there a list of all the permitted operation in the OID field (when entering via Add Bulk)? I didn't find this information anywhere...

Thanks,

Maxime