Sorry to be the bearer of bad news, but this does not seem possible. To lose 10lb in 12 days you would effectively need to lose almost 1lb per day. The average weight loss per week is usually 1-2lb - unless, as pizzle said, it is your first week, where you are likely to lose more due to water retention, etc.
for every pound you want to loose you need a deficit of 3500 calories, If the average weight loss in 2 weeks is 4 pounds you need a deficit of a further 21,000 calories that equates to 38 hours of running at 5mph over the 12 days.
Its highly unlikely hun im afraid. Anyway, even of you did lose 10lb in 12 days your body shape may stay the same hence not being able to fit into the dress anyway. Your better off using control undies as mentioned above x
Cherrycherrypinup - I would not recommend starting SW to lose a significant amount of weight in a short space of time. It is a healthy eating plan not a crash diet. However I can see that you seem to have accepted that and are looking into reasonable alternatives (I love 'hold me in' underwear ) so well done.
I would suggest either doing something else for the next 10 days to try to kick start your 'diet' or alternatively, just start SW, follow the plan, accept that you won't lose that much in that space of time but that you will almost certainly lose something and you will have started a fantastic longer term plan that will take you where you want to go if you keep on it.
My advice is to stick to plan 100% buy some sooper dooper support undies and maybe book yourself in for one of those inch loss wrap thingies-always seems to work for my mate Vicky. Maybe chuck on a bit of fake tan as well??
I borrowed a waist 'cincher' from my sis-in-law. The lable says it makes you lose 10 pounds in 10 seconds and boy does it work!! Not the comfiest but you can hardly eat when you wear it and it does wonders for your posture!
I agree with the Shred - I've got a group of girls together at work doing it - has only been a week and some are reporting 4lb and 5lb losses already mind you thats unsurprising giving the amount the workout makes you sweat!