An Unholy Mess

I am trying to verify and create new user based on Billing Statement information. The user may not be the ID of the statement but has a

relationship to that ID.

Here is the data I will be passing:

Statement PrepDate
Statement PatBal


BillTo Address
BillTo Name

Patient DateofBirth
Patient Name

relevant table info:

BILTOS
BillToID, Name (user match), Address1(user match)

STMTHIST
BillToID, PrepDate (user match), PatBal (user match)

PATIENTS
BillToID, Name (user match), BirthDate (user match), Email, PatientsID

PATWEB
PatientID, UserName (user input), PIN (user input), Question (user input), Answer (user input)

I also check to make sure the username doesn't already exist in the PATWEB table

here is what I have so far that is not working (table reference not unique - BILTOS)

INSERT INTO PATWEB (PatientID, UserName, PIN, Question, Answer, LastAccess)
SELECT PATIENTS.PatientID, 'bcolladay@pdsmed.com', 'osx5ief7*', 'What', 'green', CurDate()
FROM PATIENTS, BILLTOS
JOIN PATIENTS BILLTOS ON PATIENTS.BillToID = BILLTOS.BillToID
WHERE not exists (select * from PATWEB Where PATWEB.PatientID = PATIENTS.PatientID)
AND PATIENTS.BirthDate = '1971-05-03'
AND PATIENTS.Name LIKE 'lui%'
AND STMTHIST.BillToID = PATIENTS.BillToID
AND STMTHIST.PatBal = '215.00'
AND STMTHIST.PrepDate = '2008-03-05'
AND BILLTOS.Address1 = '987 Worley St'
AND BILLTOS.Name LIKE 'Lui@'

so I am checking to see if the billing statement and other info they supplied matches before I create the account in PATWEB.

I appreciate any help, thanks