Ok I think I understand so you'd probably want a setup like this:
Code:
tblCustomers
CustID CustName ----> other relevant fields
1 Cust A
2 Cust B
tblSites
SiteID SiteName ----> other relevant fields
1 Site A
2 Site B
tblContacts
ContID ContFN ContLN ----> other relevant fields
1 Mickey Mouse
2 Donald Duck
Then, assuming any site can belong to any customer (with multiples possible) you would then need a table
Code:
tblCustSite
CSID CustID SiteID ----> site/customer specific fields
1 1 1
2 2 1
3 2 2
What I can't tell from your remarks is if the same contact is available for multiple customers. For instance if this were a database for building inspections and you had a supervisor of a building that contained offices for many customers the supervisor would have to be attached to both the customer and the site for that location. If you do you could create a subtable for the site and put all your contacts in there, if the contacts are not site specific but they can still be part of any customer/site combination I would have a sub table:
Code:
tblCustSiteSub
CSCID CSID ContID ----> other relevant information
That where the CSID would link to the previous table mentioned.