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   GET EDITABLE FORM FIELD DEFAULT FROM ANOTHER TABLE
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   PRODUCT   :  R:BASE                  VERSION      :  3.1
   CATEGORY  :  FORMS                   SUBCATEGORY  :  FIELD DEFAULT
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   By using a lookup expression, you can give a field in a data entry
   form an initial default value that comes from another table. But if
   you want the user to be able to change that value for the current
   table, you need to locate variables instead of columns, and use two
   expressions for each column--one to look up the default value, the
   other to load the value into the table.
 
   For example, in an order form, you might want to look up the usual
   shipping address in the CUSTOMER table but still make it possible for
   the data entry operator to enter a different shipping address into the
   ORDERS table for a specific order. To do this, you need to locate
   variables instead of columns in the form for each element of the
   address (for example, VORD_ADDR1, VORD_ADDR2, VORDERZIP). Customize
   the field characteristics for each variable field to answer "Yes" to
   the question "Will new data be entered in the field?" Then add pairs
   of expressions like these for each element of the address:
 
     vord_addr1 = ship_addr1 IN customer WHERE custid = custid
     ord_addr1 = .vord_addr1
 
   The first expression looks up the value in CUSTOMER, the second loads
   the field value into ORDERS so the data entry operator can change the
   value in the VORD_ADDR1 field before it's loaded.