On a cat2950? didn't know they supported that.
Using snmp here is not very efficient.
Port security automatically learns and remembers the first mac address. No need to configure that.
I rather spend time on collecting the syslog messages from ports going disabled.
Enable an errordisable timeout so that after say 5 minutes things work again until an other mac address comes along.
And then investigate the ports going in error disable and remove the hubs.
Cheers,
Michel