Update External Database

[DMRubio]

I'm having trouble trying to get this to work right.....

UPDATE Customers IN '' [MS Access; DATABASE=C:\Documents and
Settings\Dru\Desktop\Databases\Help_Line_Tracking_MAIN.mdb] SET
Customers.CustomerID = [Customers2].[CustomerID], Customers.ContactFirstName
= [Customers2].[ContactFirstName], Customers.BillingAddress =
[Customers2].[BillingAddress], Customers.City = [Customers2].[City],
Customers.StateOrProvince = [Customers2].[StateOrProvince], Customers.Country
= [Customers2].[Country], Customers.CompanyName = [Customers2].[CompanyName],
Customers.ContactTitle = [Customers2].[ContactTitle], Customers.PhoneNumber =
[Customers2].[PhoneNumber], Customers.ContactLastName =
[Customers2].[ContactLastName], Customers.Notes = [Customers2].[Notes],
Customers.DateofCall = [Customers2].[DateofCall], Customers.ResolvedDate =
[Customers2].[ResolvedDate];

basically i have two DB, the MAIN and the USER, the user enters the data via
a form and it is stored in the Customers2 table on the USER DB which is on
the users PC, then the above query would run and append/update the data from
the enduser PC to the MAIN DB and then a delete query would remove the data
from the USER DB Reason for this is MAIN DB is on a shared drive so reports
can be run.
The USER DB exists on multiple end-user computers. I have tried linking the
tables but due to network volume it works too slowly. I have an append query
which works great but it does not update existing records on the MAIN DB.
Anyone have any idea how I can make this work?