Creating polygons based on values of other polygons

Hi,

I have a question about how to make new polygons based on the values of an attribute within existing polygons. I have a census block groups with values 0-20 (or so) and would like to group them so that the values equal 26 or as close as possible without going over. I think this could be done with a dissolve but I am not sure how to dissolve into groups like that.

Thank you for your help!