G4UserSteppingAction vs G4UserTrackingAction to change the direction of secondary partilces when primary particle decays

Dear experts,

I am an inexperienced Geant4 user. I have some doubts regarding the correct way of extracting information and changing it. My case is the following:

I have a Cs-137 radioactive source fixed at a position. This particle will eventually decay generating some secondaries. My aim is to detect just when the primary decays to obtain the electron produced in this decay and change only the direction of emission because I want it to be emitted in a certain solid angle. I don’t know if the correct way of doing this would be:

Using the UserSteppingAction, dectecting the step when the decay has been produced and access to this electron direction

Using the UserTrackingAction

Thanks in advance for your time!

Kind regards,