SAP Library - Find your answers

In continuation to what Adrian has said.
Making the SQL Query:
SELECT $[ORDR.DocDate].
Just save this query in your query manager. I would personally prefer a separate query category something like "Formatted Search System Queries". Just so that the end user doesn't mess with them inadvertantly.
Linking the SQL Query to the Delivery Date field:
Open any existing sales order. Place the cursor on the Delivery Date field so that it is active. Now press Alt+Shift+F2. This will open a Formatted Search window named as "User-Defined Values-Setup". In that window Choose the third radio button option saying "Search in Existing User-Defined Values according to Saved Query". Few more options will appear to the bottom of this option. Double click on the greyed out elongated box, just bottom to the option you just checked. It will open the query manager window. In the query manager window navigate to the query we just made and saved. After the query is added in the greyed out box. Check mark the box saying "Auto Refresh When Field Changes". In the next drop down box, choose the field "Customer/Vendor Code". Then below that finally check the radio button "Refresh Regularly".
I have referred to Customer/Vendor Code field, because, the moment you open the sales order, the delivery field will be blank. But now, that we have a formatted search, the moment someone enters the BPCode in the document, the delivery date automatically appears as your posting date.
I tested this on SAP B1 2007A and it worked.
I hope you issue is resolved.
Regards,
Kamesh __.____._