Need to Update Acc Dep and YTD Dep in Tax Book

Hi,

We need to change the Acc Dep, YTD Dep and  Life in Years of Tax Book Assets.

1) How to do this for multiple assets?

2) Also if the Dep is run for Tax Book assets, can we still change the above fields as the same is grayed out in front end.?

3) And can we change for few assets and run dep and than modify above fields for balance assets in Tax book?

Thanks in advance

Raju