Excel: Formula that updates a weight change in one cell based on monthly updates

I have 12 columns each named for a month of the year. In the row below, a trainer inputs a client's weight in the cells associated with the month they take the measurement. At the end of that row, I have a column titled "Monthly Change" where I have created a formula that takes the current month's weight and subtracts it from the previous month's weight….giving us their progress. Is there a way I can add to that formula to update that particular cell as the months progress without having to change the formula each month? I only want one cell that updates at the end of the row rather than having 12 separate cells that change with the updates. Thanks so much!

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This thread is current as of March 13, 2014.

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