------
## 最终结论
```python
def sum_range_list(lst, start, end):
    if start < 0 or end >= len(lst) or start > end:
        raise IndexError("Index out of range")
    return sum(lst[start:end + 1])

# Test cases
assert sum_range_list([2,1,5,6,8,3,4,9,10,11,8,12], 8, 10) == 29
assert sum_range_list([2,1,5,6,8,3,4,9,10,11,8,12], 5, 7) == 16
assert sum_range_list([2,1,5,6,8,3,4,9,10,11,8,12], 7, 10) == 38
```