VB/Excel developer

I have a contact program that has been developed with VB in an Excel spreadsheet. I need it to be improved and stabilsedwhich may require rewritting.
The current application is however a very good spec of what I need. In short I give each client a rating which determines how often I want to see them so that after each completed visit the application sets the date for the next contact. There are other more detailed issues but this will be easier to explain when you have the spreadsheet. So if you are interested contact me and I will send a full spec. Please let me know your rates and how do you handle support and or corrections
David