numeric fields

Hi all,
Can anyone help me to modify default theme to display additional numeric fields and later sum all the numbers?

Here is the scoop:
I am an airplane builder. FAA requires us to keep detailed log (with pictures) of all parts we build. WP seems to be the perfect tool for this with one exception. We need to keep record of how much time we spend building particular part, assembly and finally entire airplane.
Categories could be assemblies like wing and subassembly – spar, rib, or aileron etc. Time entered in each of the posts could be calculated to show how much time we spend building entire wing or fuselage. Also total time spend up to date.
It is beond my capabilities to reprogram the theme, that’s why I am looking for someone who could help me out.

George