Ah, I feel your pain. The deer in my area bed and feed in practically the same spot. Its hard to ambush them when they do this. If there is alot of sign at the cornfield but very little in the woods around it chances are they are bedding and feeding right there. Your chances are probally best if you can quietly sneak into your stand in the morning and catch them skirting the field edge before they go to bed. IF the field is small though you may have a problem getting in there undetected.