Hi Jo,

this is my suggestion, note that this is not a standard or common way of executing stock orders as by definition at some point if you want to buy a stock you need to communicate how many shares you are going to purchase. So the amount may be known only by a select group of market makers (for instance those who deal with Level III information on the Nasdaq..) and not by other market participants.
Here a reference for undisclosed amount:


buys Alaska Sky Air. In an undisclosed amount, Lunick Aviation Inc. has bought Alaska ... Inc.
(VASM: LAI) has there order form open for accepting orders for ...
www.vastockmarket.com/html/readnews.php?stock=72 - 21k

I hope it helps