Structure keeps generating random number and doesn't save values into array

I want to generate a random number with SimuTemp and save it into my messarray, same with zahler. But I just couldn't find out how I do that. I've tried printing the array out just to check if it works but it just added new random values and didnt save the old ones.

typedef struct 
{   

    double SimuTemp(double x) //Random-Temperatur-Generator von Zahlen zwischen -200 und 800
    {
        x = ((double)rand() / (double)RAND_MAX); // Erzeugt "zufällige" double Werte im Bereich zwischen 0.0 und 1.0
        x = x * 1000;
        x = fmod(x, 1000);
        x = x - 200;
        return x; // Gibt den Wert der in x steht zurück
    };
    int zahler;
    time_t secs;    
}Messwert;

typedef struct
{
    Messwert messarray[3];
    time_t currenttime; 
}Messreihe;

int main()
{
    double x= 0;

    srand(time(NULL)); 

    Messreihe M1; 
    Messreihe *PointerM1; 

    PointerM1 = (Messreihe*)malloc(sizeof(Messreihe)* 1); 
    if (PointerM1 != NULL){ free(PointerM1); }
    M1.messarray[0].zahler = 0;


    for (int i = 0; i < 3; i++)
    {
        M1.messarray[i].zahler = M1.messarray[i].zahler + 1;
        printf("Messwerte[%i]:%.1f \n", M1.messarray[i].zahler, M1.messarray[i].SimuTemp(x));
    }


    _getch();
}