How to use specified cells for hold violation fix in Encounter?

Hi everyone,

I am wondering how to use some specified buf/inv cells for hold time fix in Encounter? For example, some delay cells may be preferred. Can anyone tell me the related command?

Another question is how to specify buf/inv cells for CTS? I can choose some buf/inv cells in the CTS step. However, would Encounter use some other cells in the clock tree in the following steps?

Thanks a lot,

Tom