Returning google.visualization.DataTable from Javascript Function

Question

I'm working on a page that brings in various data from a google spreadsheet, and need to loop in order to draw multiple visualizations from multiple queries. In order to do this I'd like to run a loop which

1. queries the spreadsheet
2. alters returned data to fit my needs
3. graphs the altered data.

I've tried multiple techniques, after altering the data I haven't been able to send it back to the parent function. Is there some special technique / syntax I need to use to return the object?

Currently (for step 2) I have:

function handleQueryResponse(response) {
if (response.isError()){
    alert('Error in query: ' + response.getMessage() + ' ' + response.getDetailedMessage());
    return;
  }

//DataTable comes in is formatted wrong. Formatting for pie graphs below.  
  var data = response.getDataTable();
  var dataView = new google.visualization.DataView(data);
  var new_data_table = new google.visualization.DataTable(
    {
    cols: [{id: 'time', label: 'Time taken', type: 'string'},
           {id: 'results', label: 'Number of results', type: 'number'}],
    rows: [
      {c:[{v: 'Two days or less'}, {v:  dataView.getValue(0,0) }]},
      {c:[{v: 'Two days to one week'}, {v:  dataView.getValue(0,1) }]},
      {c:[{v: 'One to two weeks'}, {v:  dataView.getValue(0,2)}]},
      {c:[{v: 'Two weeks or more'}, {v: dataView.getValue(0,3)}]}]}, 
    0.5
  );

  return new_data_table;
}

Unfortunately, if you try to document.write the output from the function, it always comes back undefined. For example

this_data_table =  query.send(handleQueryResponse);

is undefined, even though inside the handleQueryResponse function

document.write(new_data_table.toSource());

works fine. Additionally

this_string = query.send(handleQueryResponse);

where

function handleQueryResponse(response){ [...]   return new_data_table.toString() ;}

also comes back undefined. Maybe there's something incredibly obvious that I'm missing, but this has been frustrating me all morning. For some context here is my static prototype page.