French phrase
Prévenez-moi si ~.
Meaning
Please let me know if ___.
When to use it
A polite request for notice about a change or problem. Suitable for a wide range of formal situations.
Example dialogue
Prévenez-moi si vous avez des questions.
Please let me know if you have any questions.
D'accord, je vous contacterai si besoin.
All right, I'll contact you if needed.