How to get the current time in milliseconds?

I'm working on a hacking simulation game and when ever someone connects to another computer/NPC, a login screen popups with a button on the side called BruteForce.

When BruteForce is clicked, what i want the program to do is, calculate how many seconds cracking the password is going to take based on the player's CPU speed but that's the easy part.

The hard part is i want to enter a character in the password's box every X milliseconds based on a TimeToCrack divided by PasswordLength formula.

But since i don't know how to find how many milliseconds have elapsed since the second has passed, the program waits until the CurrentTime is higher than the TimeBeforeTheLoopStarted + HowLongItTakesToTypeaCharacter which is always going to be a second.

How would you handle my problems?

I've commented the game breaking part.

    std::vector<QString> hardware = user.getHardware();
    QString CPU = hardware[0];

    unsigned short Speed = 0;

    if(CPU == "OMG SingleCore 1.8GHZ"){
        Speed = 2;
    }

    const short passwordLength = password.length(); /* It's equal to 16 */

    int Time = passwordLength / Speed; 
    double TypeSpeed = Time / passwordLength; 

    time_t t = time(0);
    struct tm * now = localtime(&t);

    unsigned short EndTime = (now->tm_sec + Time) % 60;
    unsigned short CurrentTime = 0;
    short i = passwordLength - 1;
    do{
        t = time(0);
        now = localtime(&t);
        CurrentTime = now->tm_sec;
        do{
            t = time(0);
            now = localtime(&t);
        }while(now->tm_sec < CurrentTime + TypeSpeed); /* Highly flawed */ 
        /* Do this while your integer value is under this double value */

        QString tempPass = password;
        tempPass.chop(i);
        ui->lineEdit_2->setText(tempPass);
        i--;

    }while(CurrentTime != EndTime);