Changing launch parameters during Gazebo simulation

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Hi! I am not sure if this is possible, but I have a simulated force that starts at a certain time during simulation in Gazebo (I am on ros noetic, gazebo 11). I would like to execute this multiple times, so changing this start time while the simulation is running. I am reading the parameter (double) from a launch file and I have tried reading it continuously with every timestep, however, if I change it while the simulation is running, Gazebo doesn't get the new value. I have also tried the same, but then with reading it from a .yaml file, also did not work. Is this even possible, and if yes, how?