The ui.Dialog.QueueAction() method executes an action of the current dialog. It accepts a STRING parameter, action identifier / action name declared in the dialog. For instance, ui.Dialog.GetCurrent().QueueAction("my_act").
Example:
MAIN
DEFINE f1 STRING
OPEN WINDOW w WITH FORM "ui_dialog_QueueAction"
INPUT BY NAME f1
BEFORE INPUT
CALL ui.Dialog.GetCurrent().QueueAction("queued")
ON ACTION queued
DISPLAY "queued action invoked"
END INPUT
END MAIN