Looking for changes in data via comparison

Hi,

I am looking for the correct VBA coding to be able to compare if a change has been made to my worksheet. I need to be able to alert the user, when a particular macro is run, if any changes are evident. For example, I have listed a number of companies with associated values and I need to run a comparison when I run the macro with name (eg) CompanyAccounts. The coding just needs to be able to check whether any changes have been made to the companies or values, and alert the user if it has, when I run CompanyAccounts macro.

Any help would be much appreciated