It depends on the broker/order type you're using. For some brokers, this is sufficient to send Display Quantity:
hOrder.DisplayQuantity = DisplayQuantity
Other brokers are configured differently, which require you to retrieve and set a MB field. (see documentation for the "GetMB..." functions)
As discussed offline with your account manager, we are working with you to determine the correct values to set.
I am using the Order Entry Tool in Excel that I downloaded from the site. I am using DMA limit orders