How can I make a constrained field editable?

Setting the field to OK INPUT (or maybe Entry Level=0) will make the
field editable. But, then you will need the following trick to actually
get the changed value to save because APPX always restores the constraint
field values just before rewriting the PCF record.


In Pre-Update
STORE   XXX HOLD    RECORD


In Post-Update
READ    XXX HOLD (with hold)
RESTORE XXX HOLD    RECORD
REWRITE XXX HOLD