I want to use "if" while something else is happening

So I would like to use an "if" statement while leds flash. The leds are on a delay so if I put the "if" inside the loop with the led flash then the "if" would only get triggered after the leds flash. I want the "if" to always be running while the leds are flashing on delay. How would I do this?

How would I do this?

Step 1: Post your code. Step 2: Stop writing blocking code. I am almost certain that you are using delay(). You can not do that.

Start here: https://forum.arduino.cc/index.php?topic=223286.0

K thanks for the help and yes I was using delay. I am still quite new to Arduino, didn't know there was another way.