From what I understand Pily is a Division.
I have 2 divisions on the shield Pily in Chief, and per Fess.
Here is how I believe the Blazon should go, this is probably going to need some tweaking.
"parted per Fess Ermine and Vert, a Pily Sable with three Trefoils Or in chief, an Ermine Rampant proper in Base."