Bitten off more than I can chew..?

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I want it to register an input A and then wait for 10 seconds, if another input B is registered within that time, it gives an output to the relay.

How long is the relay to be closed?

anyway:

long mostRecentInputA = millis() - 10000; 

void loop() {
  if(there's an input A) {
    mostRecentInputA = millis();  
  }

  if(theres an input B) {
    if(millis() - mostRecentInputA <= 10000) {
      send output to relay;
    }
  }
}