email message options

I have a database that is used to create and send
invoices. Unfortunately not all the invoices are paid on
time and I have to send out reminders.

I want Access to generate the reminders. There are three
different messages; please pay, please pay now, PAY!. I
have a query that sorts the unpaid invoices and I had
thought that when the first message is sent I would assign
it a number value (say 2). Then when the second reminder
needs to be sent I would have the query check the number
value and if equal to 2 then it will send the second
message. I then need it to assign a different value (say
4) so the next time it queries it would send the third
message;

Is there an easier way to do this in VB? I know what I
want to do but am not entirely sure how to program it.

Hope you follow this and any help is appreciated.