Arduino/C++ adjusting Long Millis () in loop - c++

Question

So I have made a simple Arduino circuit for practice. I am able to start and stop the loop at any moment via a button. Now I want to make some sick led light sequences.
My initial thought is changing the delay_led1 function at the end of the loop. That way I am able to change the sequence when the loop ends.
I tried to do this with: interval_led1 + 300 (marked in my code with alot of /////////) at the end of the loop, but this doens't work.
How could I add milliseconds to the interval_led1 function via the loop?
const int led1 = 13;
const int led2 = 8;
const int led3 = 5;
const int button = 10;
int ledState_led1 = LOW; // ledState used to set the LED
int ledState_led2 = LOW;
int ledState_led3 = LOW;
// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis_led1 = 0; // will store last time LED was updated
unsigned long previousMillis_led2 = 0;
unsigned long previousMillis_led3 = 0;
long interval_led1 = 500; // interval at which to blink (milliseconds)
long interval_led2 = 600;
long interval_led3 = 700;
boolean buttonstate = false;
void setup() {
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(button, INPUT);
}
void loop() {
// check to see if it's time to blink the LED; that is, if the difference
// between the current time and last time you blinked the LED is bigger than
// the interval at which you want to blink the LED.
unsigned long currentMillis_led1 = millis();
unsigned long currentMillis_led2 = millis();
unsigned long currentMillis_led3 = millis();
bool current_state = digitalRead(button);
bool prev_buttonstate= false;
if(current_state==HIGH && current_state != prev_buttonstate) {
buttonstate = !buttonstate; //reverse buttonstate value
}
prev_buttonstate = current_state;
if(buttonstate==true)
if (currentMillis_led1 - previousMillis_led1 >= interval_led1) {
previousMillis_led1 = currentMillis_led1;
if (ledState_led1 == LOW) {
ledState_led1 = HIGH;
} else {
ledState_led1 = LOW;
}
digitalWrite(led1, ledState_led1);
////////interval_led1 + int(3000); ///////////////////
}
if(buttonstate==true)
if (currentMillis_led2 - previousMillis_led2 >= interval_led2) {
previousMillis_led2 = currentMillis_led2;
if (ledState_led2 == LOW) {
ledState_led2 = HIGH;
} else {
ledState_led2 = LOW;
}
digitalWrite(led2, ledState_led2);
}
if(buttonstate==true)
if (currentMillis_led3 - previousMillis_led3 >= interval_led3) {
previousMillis_led3 = currentMillis_led3;
if (ledState_led3 == LOW) {
ledState_led3 = HIGH;
} else {
ledState_led3 = LOW;
}
digitalWrite(led3, ledState_led3);
}
}

Answer 1

Did you mean to have:
Interval_led = interval_led1 + 3000;
Where you actually assign a new value to that variable?