If you're making this just for the cranberry bars, you can go ahead and add the extra ¼ cup of white sugar that the bars call for you adding to the prepared cranberry sauce. That would mean, you'd add ½ cup of white sugar here & ¼ cup brown sugar - and you would skip the step in the streusel bar recipe of adding more sugar & heating again - and go ahead & proceed with spreading this sauce on top of the streusel crust.