Referencing the current dialog

In order to reference the current dialog, you can define a variable with the ui.Dialog type, and get the current dialog object with the ui.Dialog.getCurrent() method:
DEFINE d ui.Dialog

INPUT BY NAME ...
   BEFORE DIALOG
      LET d = ui.Dialog.getCurrent()
      CALL d.setActionActive("zoom", FALSE)
   ...
As an alternative and to simplify programming, it is recommended that you use the DIALOG keyword in the context of the interactive instruction block. the DIALOG keyword is a predefined object variable referencing the current dialog. The DIALOG variable can only be used inside the interactive instruction block:
INPUT BY NAME custid, custname 
  ON ACTION disable 
    CALL DIALOG.setFieldActive("custid", FALSE)
END INPUT