SQL Syntax Problem

Greetings,

I have a form under development that is to assign an invoice number to a specific set of records based on the client, contractor and job type.

All the above are combo boxes and the first 2 have rowsource directly from tables, no problem.

The 3rd, JobType is dependent on the first 2 being identified first. Thus the query builds from information on the loaded form.

I have built a query that obtains the data needed for the combo-box whose SQL is as follows:
SELECT [Lookup:Job_Description].Job
FROM (([Lookup:Clients] INNER JOIN [Lookup:Contractor] ON [Lookup:Clients].Client_ID = [Lookup:Contractor].Client_ID) INNER JOIN Contractor_Fees ON ([Lookup:Contractor].Contractor_ID = Contractor_Fees.ContractorID) AND ([Lookup:Contractor].Client_ID = Contractor_Fees.Client_ID)) INNER JOIN [Lookup:Job_Description] ON Contractor_Fees.Job_Type = [Lookup:Job_Description].Job_Key
WHERE ((([Lookup:Clients].Company_Name)=[Forms]![frmAssign_Invoice_Num]![cboCompanyName]) AND (([Lookup:Contractor].Contractor_Name)=[Forms]![frmAssign_Invoice_Num]![cboContractorName]));

--- hope you can read that!

I have attempted to format this so that it can be executed in code under the GotFocus event. My code, which does compile looks like this:

cboJobType.RowSource = "SELECT [Lookup:Job_Description].Job " & _
"FROM [Lookup:Clients] INNER JOIN [Lookup:Contractor] ON " & _
"[Lookup:Clients].Client_ID = [Lookup:Contractor].Client_ID " & _
"INNER JOIN Contractor_Fees ON " & _
"[Lookup:Contractor].Contractor_ID = [Contractor_Fees].ContractorID " & _
"AND [Lookup:Contractor].Client_ID = [Contractor_Fees].Client_ID " & _
"INNER JOIN [Lookup:Job_Description] ON " & _
"[Contractor_Fees].Job_Type = [Lookup:Job_Description].Job_Key " & _
"WHERE [Lookup:Clients].Company_Name = " & [Forms]![frmAssign_Invoice_Num]![cboCompanyName] & _
"AND [Lookup:Contractor].Contractor_Name = " & [Forms]![frmAssign_Invoice_Num]![cboContractorName]

But something is wrong that the compiler is missing. Can anyone find the error?

I have tremendous difficulty with sql in code. Is there any utility out there that can check syntax better than the in-program compiler?

My thanks in advance for any assistance. Right now, I am banging my head against the wall.

Regards, Sorrells