you would just make your own counter system.
create a variable, set it’s type to integer(int), then add or subtract from that variable as triggers are activated or deactivated.
below you will find the basic script that you would have in your door bp. you would also need a second switch bp where you have a reference to the door via a public variable and you will need to call the custom event open door from the switch.
though if youve never used blueprint before you may want to start with something a bit simpler. i suppose though if you have any kind of coding background you may be ok.