Grouping many Messageboxes

Question

Hi, I'm developing an application that uses an XML sheet with ID's. There are over 3000 ID's and when I start the application, if some ID's aren't in the file that were there before.. I have error checking that makes a MessageBox popup that says "ID: 12345 is not longer in DB", except if there are many it is very annoying for the user to click OK, or press the Enter key many times.

How can I make somekind of check that would not display all those messages, but rather just ONE message. (The message does not have to show all of the ID's, just a general message of text indicating there was an error finding many ID's)

Thanks in advance,

John