This file for me is a work in progress really, but I feel like I have finally got it to a point where it might be useful for you. It is actually really simple and does not provide you with anything that a scratch piece of paper and a calculator could not do. I personally just like to have my information organized and easy to update and read and have found Excel to be a useful tool to do that with some really basic formulas.
The spreadsheet file was created with Excel 2003. You will find that I set up lots of tabs, one for each room of our house. You can delete or rename each tab to correspond to your own home. You will notice that right now the sheets are set up as line items for materials to buy for d.i.y. projects. I envision that you would add a line item for each contractor that you may hire to do any of the labor for you with your finish and decorating materials below that you will purchase yourself. I.e. you may hire a plumbing contractor to redo your bathroom and many times the cost of the the tub and toilet are included in his price, but things like the towel bars and shower curtain are not.