char *pos_comma = strrchr(s, ',');
tmp->txtcheck = 0;
if(pos_comma) {
  *pos_comma = '\0';
  ++pos_comma;
  if(*pos_comma == '1' || *pos_comma == 'Y' || *pos_comma == 'y' || *pos_comma == 't' || *pos_comma == 'T')
    tmp->txtcheck = 1;
}
strncpy(tmp->toplev, s, strlen(tmp->toplev) - 1);
... the rest as normal