Excel Financial Spreadsheet Modification

I have a large excel 2003 financial spreadsheet that is almost 1/2 Gigabyte in size.? You need a computer that will house this large a spreadsheet and not get bogged down.? If you cannot retrieve it here on rentacoder, let me know and I will email you a large file transfer link for you to look at my spreadsheet in its entirety and my problem. All you will need to concern yourself is the sales portions of 20 projects, and their corresponding cost of goods sold.? The model can handle 1200 projects in detail, but I am not interested in modifying any more than 20. My spreadsheet has an algorithm that allows me to adjust when the projects start and when they finish along a time continuem.? The spreadsheet has full income statement projections, cash flow projections, balance sheet projections, depreciation schedules and tax schedules.? It is complicated in design, but very elegant.? I made it for one type of project that came on line 5 months after it was manufactured.? Now I will have many projects that will come online from 2 to 5 months after manufacture and I need to be able to handle that variable.? I have completed April 2011 Forecast columns on the sales portion, and I need help making that modification for all 16 years my model projects. If you have suggestions on redesigning things, I would be open to it.? Be careful to save your work if you try a modification.? Unless the sales cells are handled with care, the loan module and tax module error.