What ifLoad value? There is no standard MIB variable that returns
an interface "load". You have to compute it. To do so you need the
current count of traffic in and out of the interface (ifInOctets and
ifOutOctets), as well as the current time of the measurement.
You need to get both the input and output traffic counts since
the interface might be full-duplex, list a serial line. You
then do the obvious arithmetic with the samples you collected
approximately 60 seconds ago (this is why you need the current
system uptime on each measurement - to figure out what the
actual measurement interval was).
And while you're at it, you might as well check to see if
the interface is "up" or now - otherwise, the measrement
is meaningless.