SD Billing passed to Accounting Document Automatically

Hello,

We have created a custom program which helps to upload invoice with reference to sales order. In our excel we have only two fields, i.e. we enter Sales order line item and enter the qty

It automatically creates SD invoice and accounting document is posted automatically(unless there are no errors)

Now the issue is that if there is change in the price of the billed qty, as per my understanding system will allow to change the price until no FI documents are passed but only SD documents are created from conditions

Hence the question is:-

1. Is there any automatic control in SD wherein once we create an SD invoice, it will be automatically posting FI documents?

2. What are the implications of changes in price at the invoice level?

Thank You

Regards

Nishu