I would suggest using the "enter exercise" function and put in your average nights sleep and the remaining time as rest. This will give you a base line for calories burned. Then subtract 100-200 a day and this will give you some leeway for a larger meal or a day where you splurge a little.
Of course, there are some other factors involved... if you know there is an activity you do on a daily basis, calculate that in as well.
260lbs at 1/1/2009
230lbs at 1/1/2010
183lbs at 1/1/2011