Hi,
GPYoungGuns is again spot on with his SQL Trigger suggestion. I'd like to enhance the answer a bit by offering a couple of other possibilities.
First, adding to YoungGuns suggestion, instead of creating your own custom table, you can use the DUOS table, which is a table that was added to the database years ago so that you could store custom information. It's table SY90000 in the company database. I often update that table because every company has one 'out of the box'. It looks a little odd if you've not worked with it before, but many folks on this forum a very familiar with it and you can get some good advice on how to make it work for you.
If you're lucky enough to own the Extender module, that would be a perfect application.
If you have Modifier/VBA, you can write a couple of short scripts that can populate custom date fields you add directly to the Item Maintenance card. You still need a table for them to live in, like the DUOS table (or a custom table).
Another option is to use item category fields. You have 6 item category fields that you can use to store additional data for each item. It's just a string field, so you'd need to police the date format. Using security, you can restrict any additions to categories that don't exist in the table. A positive is that the values are stored in the item master table so they are available to nearly every inventory report.
There's another field in the Item Master table not visible on the windows called the Item Code. I think it was originally envisioned as a spot to store a UPC code, but right now it's not being used by Dynamics, to my knowledge. I often hijack this field for other uses. Again, this is a string field, not a date field.
This is kind of an odd one, but for strictly US clients it's doable. That's the Tax Commodity Code Field. It's not a date field either, but it's validated. So, you can populate it with real dates and your users have to pick from the menu. I use this one a lot when I want to control available values. And, no VBA or Modifier required :)
I think that about does it for tonight.
I hope this helps someone.
Kind regards,
Leslie