Customize anual depreciation

Hi guys I need to customize a depreciation key that plans depreciation only in period 12.

The asset doesn't must have depreciation in the rest of the periods.

For example If I have an asset with adquisition value of 1200 and life of 10 years , if the capitalization date is 01.01.2008,

the depreciation in period 1 must be 0, in period 2 must be 0, ...... and in period 12 must be 120 (the total anual depreciation)

Does anyone know how to customize that functionality in the system?

Thanks in advance...