Date: Chol HaMoed Sukkos 5558
From: Rabbi Moshe Sofer
To: Unknown recipient
A man hung an extra esrog as a sukkah decoration, and a villager arrives on Chol HaMoed unable to obtain his own esrog. The Chasam Sofer rules the esrog may be removed for the mitzvah of lulav, reasoning that elevating it from decoration to active mitzvah use constitutes ma'alin bakodesh.
Source: Shu"t Chasam Sofer OC §184