Integrated calculator functionality

I would like if Cronometer could build calculator functionality into food data entries. For example, when I use Adobe Illustrator, I can enter an equation into a length box (e.g. 3+2) and it will compute the value (5) and enter that as my value. I would like to be able to do the same sort of thing in Cronometer so that I don't have to keep whipping out my calculator to figure out something like "137 minus 88 grams of avocado" since I'm not too skilled at doing that sort of subtraction in my head.