From all of these suggestions (and more from another thread) I've cracked it.
Toggling an LED with ON & OFF interval potentiometers.
int timeOn = A3;
int timeOff = A7;
int Button = 4;
int led = 6;
boolean toggle = false;
unsigned long timeLedChanged = millis();
unsigned long period;
boolean ledOn = false;
void setup() {
pinMode(led, OUTPUT);
pinMode(Button, INPUT_PULLUP);
digitalWrite(led, LOW);
}
void loop() {
int B = digitalRead(Button);
int onVal = analogRead(timeOn);
onVal = map(onVal, 0, 1023, 50, 500);
int offVal = analogRead(timeOff);
offVal = map(offVal, 0, 1023, 50, 500);
if (B == LOW){toggle = !toggle; delay(200);}
if (toggle== true){
if (millis() - timeLedChanged >= period){
ledOn = !ledOn;
timeLedChanged = millis();
digitalWrite(led, ledOn);
if (ledOn){
period = (onVal);}
else{
period = (offVal);}
}
}
if (toggle == false){
ledOn = false;
digitalWrite(led, LOW);}
}
Thanks for all the help everyone!