set one's heart on - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, have one's heart set on. Strongly desire something, as in I'd set my heart on a vacation in New Mexico but got sick and couldn't go, or Harry had his heart set on a new pickup truck. [Late 1300s]