You can use Excel to do all those things, but Excel is not designed to do all those things. Excel is great for data analysis, but it is cumbersome to try to use it in place of accounting and business management software. Using the right tools, accounting software, dedicated CRM software, etc, will save you time and hassle in the long run so that you can run your business instead of trying to figure out how to get Excel to do things it is not good at doing or even designed to do.
Try a web based CRM or Accounting solution as I think they are the most progressive, secure, and scalable (Nolapro, NetSuite, etc.).
Shane Eloe, CPA