Nome,
If you mean you just want this to happen at the point of when you are
entering the record, this will be easiest to set up if you use a Form
for your data entry/editing. Then, on the After Update event of your
Expiry Date control on the form, you can put code something like this...
If Me.ExpiryDate = Date Then
MsgBox "Red alert!"
End If
If you mean you want it to alert you when you access the record, there
are a couple of ways, I suppose. One is to put code similar to the
above on the On Current event property of the form. Another is to use
Conditional Formatting, which you can set up on the ExpiryDate textbox
to show in a different colour if it's today's date.
If, on the other hand, you mean you want Access to prompt you when you
first open the database, or some such time, of the existence of any
records that meet the alert criteria, you could use code like this on
the Load or Open event of a form which always opens when the database
opens...
If DCount("*","YourTable","[ExpiryDate]=Date()")>0 Then
MsgBox "Red alert!"
End If