This invention relates to a method for dynamic insertion of a computer code processing within a running computer task in a transparent fashion for this target task. It also relates to a method using such a dynamic insertion in order to execute a multi-task application in a virtual container forming a virtualized environment session. This method comprises the following steps of storing by a manager task of a hooking datum representing the code processing to be inserted; executing, within the execution of a system routine called by the target task, a hooking instruction initiating a test of the hooking datum; and executing the inserted code, according to the result of said test and instead of the program instruction following the hooking instruction in the execution of said system routine.