how to pass the variable to the categoryNames in GPU coder?

In the main.cu file, I defined a array below. I wanted to pass a variable index to replace 0. Can you suggest how to do it?

coder::categorical out;

coder::categorical* labels_data;

labels_data = &out;

int *indx = (int*)calloc(sizeof(int),3);

targetFunction(inImg.data, &out,indx);

emxArray_char_T_1x6 label = labels_data->categoryNames.data[0].f1;