Same Data, Different Criteria, One Report!?

I am trying to create a tax report for my business and am not very familiar with Access beyong making basic reports from a single table and query.

Here's the problem:
I want to report total costs for my unsold inventory purchased and worked on prior to 2005. From that I want to be able to subtract the total costs of sold inventory purchased and worked on prior to 2005. Yes, all in one report. Is this even possible?

My report contains these columns from a single table-
inventory #, purchase date, cost, sold or unsold (yes or no check box), 3 columns of additional costs and 3 columns of cost dates. Also a couple other confusing columns of costs that were split between myself and co-purchasers. These include a column of negative costs, the date paid, the balance paid to the co-purchaser, and the date of the balance paid.

I have been sorting by purchase date prior to 2005 and unsold.
The problem is I have no idea how to include the values of the sold inventory in with this report of all the unsold inventory costs without creating a massive report with all my inventory from which I can not sum the columns properly.
The other problem is that when I sort by purchase date I get cost dates from after 2005. I can limit the criteria for one of the date columns, but not all.

My questions are:
How do I included both sold and unsold inventory information in a report and sort by inventory # without simply listing all the information together in one column by inventory #? Can I do the calcualtions I want to do in one report?

How can I limit all of the date columns to show only before 2005? If I make each of the date columns with criteria AND >#12/31/2004#, they limit down to only a few records because many of the date fields in my database are empty. If I use the OR criteria it doesn't work.

I actually have many other questions but I suppose those are the biggest ones.


I know that this is a very specific topic, so if anyone has suggestions as to great resources for Access help (ie. books, tutorials, etc.) particularly with creating tax or inventory reports from a single table, that would be extremely helpful.
Anything would be extremely helpful!! I'm sunk.