Excel export with RowGroup

I found this question asking about exporting tables using the RowGroup extension with each group on a different sheet interesting. The question asked about using the Add a new sheet example. This example was created from code that F12Magic posted with a couple bugs fixed by others on the forum. Combining the final fixed example along with some code from this thread to customize the Sheet1 output resulted in this example:
http://live.datatables.net/hemelesi/1/edit

The rowGroup.dataSrc can be configured to support one or more levels of grouping. This example supports exporting only the first group. The multiSheet boolean variable controls whether the export is on one sheet or individual sheets for each group.

The example supports these standard button options:

        title: '',
        header: true,
        messageTop: 'This is the top',
        messageBottom: 'This is the bottom',
        sheetName: 'Single Sheet',  // This is only used in singe sheet mode
        footer: true,

        exportOptions: {
          modifier: {
            search: 'applied', 
          }
        },

Use any desired selector-modifier. The above is just an example.

The only setting needed inside the customize function is this varaible:

multiSheet = true;  // Export all groups in one sheet or multiple

Please make improvements to the code and post them here if you do.

Kevin