LVA Main Asset number capitalization to be deactivated

Hi Experts,

We are planing to start the Low value asset,I have configured below mentioned steps in the testing client.

1.New Asset Class

2.New Number range

3.Period control 01/01/01/01 because we have to depriciate immediately(Base Method) and to dispose immediatly(ABUMN).

4.New depr.Key for immediately.

5.LVA amount 3000

User requirement for maintain LVA.Main asset to create with department wise sub asset for department assets.Exp IT is Main asset code 1000-0,Printers,card readers 1000-1,1000-2 etc.. all IT asset will come under sub asset number.Because in this way they can easily get the departmet wise report.

Now i want to do the configuration if the user mistakenly by using LVA main asset number for posting system will not be allow .becuase if he used main asset numeber for capitalization the capitalization will copy to sub asset number.

Anybody can suggest how i can achive above mentioned scenario.

Regards,

Nivas.