How convert oid value (string) to interger

Hi,

I'm trying to create a monitor for the current temperature for a netapp controller, the oid that I'm using is this one:

enclTempSensorsCurrentTemp 1.3.6.1.4.1.789.1.21.1.2.1.25

It returns a string value like this one: 18C (64F) ambient, 26C (78F), 26C (78F), I would like to make an alert based on the ambient temperature.

I'll appreciate any suggestion.

Regards.