Issue Connecting Form To Table

Probably a newbie-esque question. But here goes.

Background Story: (Not overly relavent)

I decide I want to make a quick Database to merely keep track of a few job details. My use only mainly. Well the new guy decides that to get in the good graces of the production manager we're going to track all this other stuff with it and make the data easy to enter so anyone can do it. Well apparently HE bit off more then WE can chew. And now it's a matter of US working on this by HIM looking over my shoulder as I muddle my way through this. So now I turn to experts for help....

The Problem:

What I've got is a form that allows me to enter a variety of info on the projects we're doing. Nothing special. What I now need to be able to do is enter time employees spent on this job so we can better track how much each department spent on it. The problem is to enter the time ATM we have to rummage through every person's time sheet on a particular job and add all the times and enter it. This is sort of a grueling task at best and leaves ample room for error. What I'd like is another form specifically for entering the time. Chose the Job # from a drop down menu. Then chose which piece of the job from the drop down menu. From there I'd like to merely be able to select which department, (Also via drop down menu I suppose). And then merely have a box in which you enter a dept time and it ADDs it to the time already in the table for that dept. That way it should be easy to go through one employees time sheet, enter all there times and then go to the next one and have it added to a total dept time value in the table. Probably not overly complex. Merely beyond my limitations in Access.

So as an example.

All the data is entered on the project itself aside from time.
So I want to be able to look at Mike's time sheet and say ok he worked for 2 hours on job # 4434 Unit 3. Pick #4434 from a drop down menu. Have the second menu sort to know that there's only Units 1,2,3, & 4 on Job #4434. (Got this accomplished.) Be able to pick a production department, let's say graphics. Enter 2 hours. And then when I get to Eric's time sheet I want to enter his time on that Job# and Unit# and have it added to that 2 hours giving a total department time. Got that? Any help or insight anyone?