Make it wanna jump out the front

Maybe first couple of times feed it in the box. Personally i do not like feeding dogs in the boxes but in your case the dog is sitting so this will make the dog stand up in there, as they do when eating.

If he/she is a mad killer, grab a ''stir up'' and have it inside the box at the grill. Make sure you have it tied up so the dog doesnt pull it to the back of the box then pull it out makig the dog jump out.

Do that twice then next time wave the stir up outside the box by the grill, then go for a run having someone open the lids so the dog runs straight for the stir up.

Do that once or twice a week then the day before you trial next - and see how it goes.

Always worked a treat with my kiddos - but when ive used this method its been for dogs turning in the boxes, not for the sitters.