By default, a Validation Checkbox widget is set to require a selection. If you insert a number of checkboxes on your page, however, you can specify a minimum and maximum selection range. For example, if you have six checkboxes within the span tag for a single Validation Checkbox widget, and you want to make sure that the user selects at least three checkboxes, you can set such a requirement for the entire widget.
<script type="text/javascript"> var cb1 = new Spry.Widget.ValidationCheckbox("checkboxwidget1",{minSelections:value, maxSelections:value}); </script>