You need to use the message.getCount('/) to get the row count. Then use a for loop to iterate over each row.
//Get the rowCount and then loop through each.
var rowCount = message.getCount('/');
qie.debug('rowCount: ' + rowCount);
//This for loop is what will allow you to get each row.
for (var j = 1; j <= rowCount; j++) {
//nodetag syntax = Begin Index, Width [ Row Index ]
qie.info('col1: ' + message.getNode('2,5[' + j + ']'));
// so this starts at column 2 and goes 5 spaces. j defines what row to get.
qie.info('col2: ' + message.getNode('12,8[' + j + ']'));
// so this starts at column 12 and goes 8 spaces. j defines what row to get.
}