Automatic Update Ship Date

Example of our issue: If we add a new item to an old sales order without changing the ship date and if we are almost out of stock on the item (On Hand - Sales Orders) and this order will take it below what we have on hand it will not always show up as out of stock because it will fill the older ship dates first.

What we are looking for: Is there a way to set up the “Ship Date” on a Sales Order to auto default to current date when adding new items to an older sales order.

Thank You for any suggestions you may have.