1. A handheld device having a user interface capable of selection of mathematical object of a more complex mathematical object comprising: a screen capable of displaying at mathematical objects and a cursor; a key panel having keys at least capable of selecting positions of said cursor and moving said cursor horizontally or vertically on said screen; a processor for executing programming that provides a user interface to allow a user to perform the following steps: a) scroll the cursor to a valid mathematical object in a history display, b) activate a sub-expression mode having a selection box, c) size and position the selection box over a valid object, and d) copy the object.