I *think* I understand the question now, having re-read it.
exclusion of 'land value' from that basis
The TurboTax program does that, if you enter the data correctly. When you first enter the property in the Assets/Depreciation section, you are asked for two values. The first value is the total cost of the property in it's entirety. That goes in the box labeled "Cost". The second value goes in the "Cost of Land" box, and the value you enter there is how much of the amount you entered in "Cost" is allocated to the land.
The program then does the math by subtracting the cost of land from the cost, and the result is the amount to be depreciated over 27.5 years.
