Using millis to add 1 minute relay delay

first of all, i'm doing prevent solenoid turning on , off , burning out.

i'm making thermostat kicks on solenoid+relay when realtemperature goes below settemperature , i'm having trouble coming right code give solenoid 1 minute delay after hits settemperature before coming on again.  reason, code doesn't seem working... thoughts?

code: [select]

void relayswitcher(int realtemperature, int tempsetting, int relay){   
  unsigned long currentmillis=millis();
  unsigned long interval=60000;
  unsigned long previousmillis = 0;
  if (currentmillis - previousmillis >= interval){
    previousmillis = currentmillis;
      if (actualvalue < slidersetting) {
        digitalwrite(relay, high);
        } else {
        digitalwrite(relay, low);
      }
  }
}

quote

unsigned long previousmillis = 0;

put above void setup() area. need keep it, otherwise resets everytime

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