I found standing up nappy changes worked better when DS started doing this. Toys or other distractions can also help. Promising to give DD some milk after seems to work here (for now!)
Do you use cloth or pull-ups? I saw a mum at swimming on Saturday dressing her DD standing up and she used pull-ups, it was so easy! Can't get it to work with cloth at home though. Either that or DD is still too young and wriggly lol.