Add Single Record To A Table Using Append Query With One To Many Relationship

I have tables Account (PK acctnum) and Orders (linked via acctnum to Account). There are multiple orders per account that need to be billed individually. When creating an invoice I need to add the Account to the Invoice table and the Orders to the InvoiceDetail table. I use 2 queries to accomplish this. The first one though adds multiple records to the invoice table (because of the one to many relationship). I need to keep that so I don't bill anyone with no orders.

INSERT INTO Invoices ( InvoiceDate, AcctNum )
SELECT DISTINCT Date() AS InvoiceDate, Account.AcctNum
FROM Account INNER JOIN [Order] ON Account.AcctNum = Order.AcctNum
WHERE (((Order.OrderNum)=[Forms]![Account]![Order].[Form]![OrderNum]) AND ((Account.BillingCycle)="on discharge") AND ((Order.EndDate) Is Not Null) AND ((Order.Closed)=Yes) AND ((Order.PatientName)=[Forms]![Account]![Order].[Form]![PatientName]));

Is there any way to get it to only add one record? I've tried limiting it with several parameters to no avail.