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Writing a New CHOOSE-FIELD or SEARCH-FIELD Trigger for a Procedure Parameter
When a parameter is defined as an input column, if the column has a target form and that form has CHOOSE-FIELD or SEARCH-FIELD triggers, those triggers will be imported to the input screen.
You can also write a specific CHOOSE-FIELD or SEARCH-FIELD for the procedure. Your trigger can contain references to any input value specified by the user within the same procedure step. For instance, if the procedure step contains an input parameter called CST, its value will be stored in the :PROGPAR.CST variable. This is useful, for example, if a given procedure step contains an input column for a Sales Rep and another input column for a Customer, and you want the Choose list for the latter column to display only those customers that are associated with the specified sales rep.

זה אומר שב-CHOOSE-FIELD שלך, צריך לכתוב WHERE CUSTOMERS.CUST = :PROGPAR.CST