relationships/ tables

Hi

Using Access 2007.

Despite lots of reading around the subject, relational tables seem to be a
real block and this is causing issues with trying to set up forms that work
:-( I have set up forms that have taken data from two tables and that has
worked reasonably OK. However, I realised that I had 2 many-many tables and
that this might be the cause of some of the problems I encountered (data not
showing up in forms) - so I added what I hoped would be a junction table that
would resolve the issue.

The scenario:
tblContacts - includes contact details for mailing list, attendees of
events, billing contacts. Contacts may have no links with events - or have
attended several.
tblEvents - includes all details for organisation of events. Events may link
to several attendees.
tblBilling - the junction table. This includes the ContactID and the EventID
- both PKs in their own tables and then things like Invoicing. Each bill will
relate to one Contact and one Event.

The Contacts and Events were based on the templates that come with 2007 -
though the fields have been changed quite a bit. I have played around with
the database as I have been learning so will need to review it before
embarking on the final (hopefully) version, but at the moment the Tables look
like this:

tblContacts
Contact ID - AutoNumber
Title - Text
FirstName - Text
LastName - Text
Company - Text
JobTitle - Text
etc for Add1-4/ E-mail address (Text)
Telephone numbers, etc (Numbers)

tblEvents
EventID - AutoNumber
DateofEvent - Date/Time
EventTitle - Text
etc for Start/ end times/ Rooms required/ Catering
It also had ContactID but then I ended up with 20,000 records (presumably
evey contact attending every event!)

tblBilling
BillingID - AutoNumber
EventID - Number
ContactID - Number
CostperPerson - Currency
etc for Invoiced (Yes/No)/ DateInvoiced, etc.

The Relationships (set up using the tools in Database Tools) are
Contacts (ContactID)1:Billing (ContactID) Many
Events (EventID) 1:Billing (EventID) Many
(This feels as if it should be different but I can't see how to change it!)

I've done things like Rule validations and they come up as OK.

One error message I get when I try to add a field (say Contact.Title to
form:Event Details) is that "To complete this operation Access must modify
the RecordSource property of the current form... that it will create a new
query and the form will no longer be based on the Current Events query..."
This happens even if I set up an entirely new form with no relationship at
all to the Current Events query!

Hoping that something really obvious is the problem and that it's easy to
sort out! And even if I have to start afresh with the final version of the
database, I would really like to get to grips with where I'm going wrong with
relating tables!

Many thanks