How to pass double data to analog output pin of DAQ

Hi, I am using USB 205 MCC DAQ. It has 2 analog output pins. I want to transmit 2 data's, 1x256 data to analog output pin 1 and 1x12 data to analog output pin 2. I tried transmitting 1x256 data to analog output pin using a mex file and It works well

    int		ch1 = 0;
    int		Row1, Col1;
    int		Chan1, ExitFlag;
    int		NumAOChans, dummy1;
    float	EngUnits, voltsSent;
   int		ChannelType1 = ANALOGOUTPUT;
   char	rangeName[RANGENAMELEN];
for (i=0;i<N;i++) 
    {
//     mexPrintf("\nThe output is %f",data[i]);
      ULStat = cbAOut(BoardNum, Chan1, Range, data[i]);
       
      ULStat = cbAIn(BoardNum, Chan, Range, &data[i]); 
//  mexPrintf("\nThe output is %f",data[i]);
  bb[i] = data[i];
    }

I tried changing the channel number in the above code, but that crashes matlab.The above code is from Universal Library C program examples. I dont know how to transmit the second data to analog output pin 2. How to change the channel number in the mex program?