Handling Exceptions

[ads086]

Hi All

Need some help with this little project I have to do.
Firstly, yes, it is an assignment, BUT, the assignment is basically to do whatever you want, the only requirements we have been given are to use ASP.NET with VB.NET, and it must connect to an Access database.

Table A contains a primary key, which is foreign key in table B. The primary key of table B is a foreign key in table C.
Now, since I'm only starting on the development of this site, I havent got a huge amount done. Right now I have pages to administer Table A and Table B, with Table B using the QueryString to determine which ones to extract from the database.
Now, what I need to do is to have a page appear, or even just an error box, that stops the delete occuring should somebody click the Delete button in the GridView on page for Table A if it is referenced in Table B. ASP.NET throws an Unhandled Exception error, which it should, but I want to handle the exception. But I don't know how or where I should be looking.

Any help is hugely appreciated.
Thanks