What can I add to my function that will make sure only numerical input is added? This is not for homework.

Code:
float num_check (float num_entd)
{
    while((num_entd>1000) || (num_entd<0))
      {
            printf("Please enter a valid weight between 0 and 1000 lbs\n");
            scanf("%f", &num_entd);
      }
return num_entd;
}
Thanks