Troble Reading Vibration Sensor

Okay, I have been going over the blinkwithnodelay code again. And as far as I can tell, there is nothing on in the code that will help solve me problem.

The line of code unsigned long currentMillis = millis();

Returns the millis

The line of code

previousMillis = currentMillis;

updates the previousMillis to what ever the current mills reads

The line of code

currentMillis - previousMillis > interval[code]

compares the difference between the currentMillis and the previous millis and if it is greater than a thousand the led flashes on.

This program works great for flashing a LED it doesn't work for creating a countdown timer.
If you do the math, currentMillis - previousMillis always equals 1001.

I am trying to countdown 90 seconds from when the loop in my program starts. So I need to read the mills at one point in time and hold it as a static value so that I can figure out when 90 seconds have passed.

I am sorry, but I really don't see how blink without delay helps me solve my problem.