Alert Rule

Hi All,

can any one provide the setup for following scenario

whenever the SO is modified by any user, system should notify the alert to the person who created SO.

Example:

SO1 is created by User1 and SO2 is created by user2 and SO1 is modified by User4 and SO2 is modified by User5. in this case alert should notify alert to user1 for SO1 modification and user 2 for SO2 modification.

it has to consider SO created by user id, based on that alert is required.

Thanks.