Do you want to share your project file? It would make it easier for us to see what you are trying to do and provide help.
You should be able to use the timer behaviour along with some variables to make this work. You could also use the every 'X seconds' action.
You could have a boolean variable called "controlswitch" and then use every X seconds toggle "controlswitch".
Then you would have an event that says if "controlswitch" is true, set the controls active for your first character and inactive for second, and another event that says if "controlswitch" is false, set the controls active for your second character and inactive for first.