Adding item to array once when function is called multiple times?

I want to add a channel to an array of channels if its level is above a threshold, this function is the delegate callback for providing the channel level.

This fucn is used constantly to provide level data, however On init i want to add the channels above the threshold to an array. However then i dont want it to add them again, just 1 instance of each channel that meets the criteria.

I wanted to use this code and check if the channel i receive data from is already in the channelArray, if it isnt, then add it and if it is then skip over it...However its not calling / working.

Can anyone help me with the approach to this? Issue is each channel calls this func every time its moved, so i need it to just run the code to add to array a single time.

- (void)cdcControlDidReceiveBusSend:(NSInteger)channel withValue:(float)value forBus:(NSInteger)bus onModule:(NSInteger)module {
    NSNumber *recievingChannel = [NSNumber numberWithInteger:channel];
    NSLog(@"RECIEVED SEND DATA FOR CHAN:%ld VALUE:%f FORBUS:%ld", (long)channel, value, (long)bus);
    if (value != -80.000000) {
        NSLog(@"CHANNEL:%ld FADER IS UP ATTEMPTING TO ADD TO FOCUS ARRAY", (long)channel);

        for (NSNumber *arrayChannel in self.focusChannels) {
            if (recievingChannel == arrayChannel) {
                NSLog(@"ALREADY SAVED THIS CHANNEL...SKIPPING");
            } else {
                NSLog(@"ADDING CHANNEL %ld", (long)channel);
                [self.focusChannels addObject:[NSNumber numberWithInteger:channel]]; // add the channel number to the array of channel numbers if the fader is up
                NSLog(@"FOCUS ARRAY NOW CONTAINS %lu CHANNELS", (unsigned long)self.focusChannels.count);
            }
        }

    } else {
        NSLog(@"CHANNEL:%ld FADER IS DOWN NOT IN MIXFOCUS ARRAY", (long)channel);
    }
}