Silly question for those experienced w/ broodmares

Okay, I have a "silly" question---one not answered in books (that I have found.)
For those of you who have had broodmares in the past, would you please share w/ me when you could feel (or see)the foal move? I have a very large and big-barreled mare and this is my first time with a pregnant mare------I swear I would pull a Tom Cruise and purchase my very own ultrasound machine if I had that kind of $!! I am more nervous about my mare's pregnancy than when I had my own!