The function replaces the second occurrence of a specified character in a string with a different character, but only if the string contains at least two occurrences of the specified character.

[CODE]:
```python
def approximate_function(string):
    char_to_replace = 'l'
    replacement_char = 'e'
   
    if string.count(char_to_replace) >= 2:
        second_occurrence_index = string.index(char_to_replace, string.index(char_to_replace) + 1)
        string = string[:second_occurrence_index] + replacement_char + string[second_occurrence_index + 1:]
    
    return string
```

Let me know if you want to test more inputs or if there's anything else I can assist you with.