Posting this in hopes that it will help others. At least as of v1.8.1 of datepicker, using ‘window.DP_jQuery.datepicker’ no longer works, because the pointer(right term?) now is named with a timestamp of its creation – so for example it would now be ‘window.DP_jQuery_1273700460448’. So now, rather than using the pointer to the datepicker object, refer to it directly like this:
$.extend($.datepicker,{_checkOffset:function(inst,offset,isFixed){return offset}});
Many thanks for the answer below for getting me what I needed.