Hong Kong Tax Depreciation

My question relates to Hong Kong Tax Depreciation:

Example: 

An Asset is purchased in year 1 for 100,000

In the first year, a 60% Bonus Rule Depreciation is allowed; also, in the first year, the Asset is depreciated at 20%...NET after the Bonus Rule...

Asset Year 1

Purchase - 100,000

Bonus -        60,000

Depreciation 40,000 * 20%, or = 8,000

Total Year 1 Depreciation = 68,000

Then, in Year 2, the depreciation should be calculated on the remaining amount, or = 32,000 * 20% = 6,400

Then, in Year 3, the depreciation should be calculated on the remaining amount, or = 25,600 * 20% = 5,120

Each subsequent year the asset is depreciated likewise...

Any thoughts on how to accomplish this? 

Thanks,

Michael