Auto-prompt to reorder?

I have a client (he's a physician) who sells medicine on his website. He's interested in having some kind of system in place that will look at a customer's order (the date it was placed) and then send reminders to the customer when it's time to reorder a refill. So, say someone buys a bottle of medicine A on May 31, and it has 30 "take once a day" pills in it. They want a reminder email to be sent 25 days after the order so they can remember to get the refill before they run out.

I'm not even sure this is possible, because it would require calculating the dosage amount in every single bottle and determining the date of purchase for every bottle purchased, and then having something in place that will email each customer individually. I haven't seen a mod for this, so I'm guessing it's something that will need to be custom-scripted. Frankly, I don't even know if it's worth it to custom-script this...but I digress.

Does anyone know of a mod that will do this? If not, how about the best ways to go about pulling this off? (Or even better, reasons why I should talk them out of this?) Any help or enlightenment would be appreciated. Thanks!

It's a great idea that would be useful for a lot of sites which cater mainly to repeat customers, but there's no existing mod I know of. Maybe the doctor would be willing to fund a post in Commercial Help Wanted.

Thanks Steve. That's what I thought. The client wants me to code this for them, but I think it's out of my abilities to do soemthing like this. If they are insistent, then I'll probably direct them to someone else :)

Thanks again!

If you have the time, you could post a request in the Commercial Help Wanted forum and, if you get an workable response, present the client with a completed project with the cost of the mod added in.