void ADD_QUOTE(){
     do{
        printf("\nPlease enter Length:\n");
        scanf(" %d ", &length);
            }while(scanf(" %d ", &length)<200 || scanf(" %d ",&length)>4000);
       {
        while ((length[count] = getchar()) != '\n')
            putchar(length[count]);
            }
            return;                   
    do {
        printf("\nPlease enter Size:\n");
        scanf(" %d ", &size);
            }while (size[count]<200 || size[count]>4000);

    do {
        printf("\nEnter which Board type you want: 'A'-4mm Standard, 'B'-4mm Thickened, 'C'-6mm Standard, 'D'-6mm Thickened:\n");
        scanf(" %c ", &types);
            }while (types[count] == 'a' || types[count] == 'A' || types[count] == 'b' || types[count] == 'B' || types[count] == 'c' || types[count] == 'C' || types[count] == 'd' || types[count] == 'D');

    do {
        printf("\nPlease enter Quantity:\n");
        scanf(" %d ", &quantity);
            }while (quantity<0);

  while(getchar() != '\n');
  numberboards++;   
}

Ummm, before you guys say anything, im a yr11 at school who reallys needs help with this code...
im trying to add a input validator but i cant find anything online

if you need to see the full code it is linked on the bottom...
(although it would really help me if you could tell me what is wrong with it) =)

Thanks

}while(scanf(" %d ", &length)<200 || scanf(" %d ",&length)>4000);

that should be length<200 || length>4000

im trying to add a input validator

the simplest thing I can think of are using if-else statements