E-mail approval of an operation?

I am working on a project that has many users having different roles (manager, employees etc.) and for ex. when an employee needs to make a change on the data, program should automatically send an e-mail to the manager for the approval of the operation. If the manager approves the operation then the employee will be able to make the change, otherwise he/she won't. I am not using SharePoint or something like that to manage workflow, so i am thinking about using a web service to manage this task. In other words, program will send an e-mail to the manager and when the manager approves or denies the operation it will invoke a web service and then us开发者_Python百科er will be able to make change on data. But i don't know how to invoke a web service over an e-mail, or if there is another way to manage this task.

Any help would be greatly appreciated

You don't need to invoke a web service over email - just provide a link that the email receiver can click on, which loads some page which updates the database to say that the operation is approved (or however the approval works in your system).