Grab chart object using containerId

[AL]

Hello,

How would I grab the chart object I'm using if I was to use the containerId? 

The pie chart is: 

chart = new google.visualization.ChartWrapper({
                'chartType': 'PieChart',
                'containerId': myContainer,
                'options': {
                    'pieSliceText': 'value',
                    'legend': legend,
                    'chartArea': {'left': 20, 'top': 10, 'right': 10, 'bottom': 20},
                    'pieSliceText': 'value'
                }
});

This code section is run many times to create multiple charts. Therefore, "chart" would keep changing to the most recent chart created inside different divs, so I can't just call chart.

How would I grab the specific chart if I have the container div?

Thanks.