Change in Life - Calculate Depreciation based on NBV

We need to change the life of  multiple assets and want the depreciation to be calculated based on Net book value and don't  want depreciation to be calcualted retrospectively.. If life of asset is 5 years and asset cost is 100 and 3 years have passed by and accumulated depreciation is 60 and Net book value is 40.. now I want to increase the life by 2 more years, I want the depreciation per year should be 10.. 40 divided by 4..