Need to bulk edit a checkboxes field without clearing current choices

Hello all,

I would like to bulk edit a checkboxes field (4 choices) that already contain information (1 or more choices already selected) by checking an additional choice, without clearing the field.

The following post (and solution) seems to be very close to what I need:
http://help.zoho.com/portal/en/community/topic/suggestions-for-bulk-edit-of-multiselect-field?-6-12-2009

This is for a multiselect field. Could it be adapted for a checkboxes field?

Thanks in advance,
Patrice