Catching user bad input in query

[Oblivion_Creed]

Im working on a small library project in which i have an input that takes user ID and the book he want to take.Now books has ages for reading and some young user cant take certain books. now i want to raise an error to the user every time he try to take a book that not for his age and that he will be able to correct his input.How can i do that?

[alansidman]

Tell us what your tables look like.

[Oblivion_Creed]

Tell us what your tables look like.

as you can see i have here two query's: One that add information to a table and the other that delete information from the old table.
i want to combine those two in to one query that add and then delete information.

[June7]

Instead of catching an error, set the combobox RowSource SQL to only offer books appropriate to the student age. However, conditional combobox with lookup alias will not work nice in continuous or datasheet form. Review this recent thread on same topic https://www.accessforums.net/showthread.php?t=67549