Update On Hand Qty Field in Quantity Adjustments

I am trying to get a custom date field to update with today's date in the Quantity Adjust field after a bin is adjusted.  The system does update the On Hand Qty field but I am not able to get my field to update without clearing the form and reloading the part number.  How does Epicor get the On Hand Qty field to dynamically update and is this doable with a script?  Thanks,