update_acct_invoice_m Guide

The update_acct_invoice_m API updates invoice custom fields custom_status_label, custom_status_desc and client_notes.

API Specification:	update_acct_invoice_m
Required Fields:	<client_no> <auth_key> <acct_no> or <client_acct_id> <client_acct_id> <src_transaction_id>