multiple payment terms on invoice

Hi.

We've been putting out multiple invoices on sales order with multiple payment terms but would like to start issuing just one invoice for a sale.  Multiple payment terms example -- Net 30/60/90/120.  This particular terms means customer can pay in four installments -- the first installment is due in 30 days and the last installment is due 120 days. 

Does anyone have a creative solution how to invoice for this in Great Plains?  We have so many of these special terms that it has become a bit cumbersome and inefficient to generate multiple invoices.  Plus, I would like to start using Itergration Manager to generate invoices instead of entering invoices manually.

Thank you for any help you can give me.

Best regards,

Loan Nguyen

CyberCoders