EX MARKS THE SPOT  Retired rodeo rider Jessie Leigh has one more trick to pull off: partnering with ex-husband Payson MacCormack to save her ranch. Hope's Ride offers horse therapy for children, and Payson is a pediatric surgeon at the hospital set to certify the program. Their split wasn't exactly amicable, but Jessie's determined to make it work...even if Payson's presence sends her heart racing.  With a promotion on the line and a passel of kids in desperate need of Hope's Ride, Payson should be focused on prepping the program for the hospital's review. But he can't concentrate on anything but Jessie. Payson's career and Jessie's ranch are depending on each other, but will working together bring the surgeon and the cowgirl closer together, or drive them apart for good?