Excel is one part of the productivity suite of software from Microsoft, Office. As a spreadsheet application, it`s focus is on storing data in rows and columns.
Invoicing data, customer contact data can all be stored within Excel, however Excel is not an invoicing or CRM solution. It sounds like you are interested in a complete CRM solution.
Depending on your requirements, budget, goals, and overall situation different solutions will be appropriate for you. Some of the more popular solutions are:
http://www.salesforce.com/ Hosted online CRM services (perfect for a smaller business)
http://crm.dynamics.com/ Microsoft Dynamics (several versions to choose from) - great for medium sized companies
http://www.oracle.com/siebel/index.html CRM from Oracle for larger, Enterprise businesses
http://www.sap.com/usa/index.epx CRM for the top 100+ Fortune 500 companies
Again, there are many undisclosed variables that will determine which solution is best for you. What I recommend is that you consult with a small business technology expert, like a Microsoft partner (you can find one using http://www.microsoft.com/smallbusiness/hub.mspx)
Also, the Wikipedia page for CRM solutions should prove useful: http://en.wikipedia.org/wiki/Customer_relationship_management
Microsoft Small Business