1. A method for dynamic insertion of one or more program instructions by a first computer task, termed manager task, in a second computer task, termed target task, executed in a memory address space managed by a system software in a computer system, comprising: storing, within a memory area outside the memory address space of the target task, of at least one hooking datum representing initiation data for the code to be inserted; executing, within the execution of a system routine called or controlled by the target task, an instruction termed hooking which initiates a test of the hooking datum; 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; wherein the target task is linked to a third task belonging to a same session of a target application by the sharing of a single execution memory space and represented by a common virtual container identifier, and wherein the target task and the linked third task are temporarily blocked from execution during the loading, into said single execution memory space, of the code to be inserted by sending a STOP signal to the target task and the linked third task.