Thank you for the quick response,
I think you are rigth, i need to clarify better my problem, i started from scratch the Tutorial, and i placed all blocks according to the Tutorial. After that i clicked on "generate the flowgraph". Once i did this in the folder where the GRC is saved Python file was created. I opened this file to edit it as proposed in the section 3.1.5 of the Tutorial and wrote the lines that in the tutorial said should be added to make Flowgraph work taking into account the two signals. I did this, i wrote the new code i saved it on python (the same file), and then i clicked again on "Generate the flowgraph" hoping that the "flowgraph" will take the changes on the python files, but it did not happend; what it happend is that it created again a Python file overwritting the one the one that i did changes on. i am kind of lost. How can i make the flowgraphs to take Python script once it have change it?