A simple approach is to add a subtable with a date/time field with default set to now() and a text field to contain the comment.

Whenever you need to comment, add a record to the subtable with the commment and it will have a timestamp against it.

You can then sort the comments in date order from the parent (customer) table, and even include this table in a print report to print a full activity history.

When you say insert reminders, do you mean have a notification email/message pop up to a user?

Might be easier to take this conversation off the forum - feel free to send me an email at hello@danjamesmedia.com