BPC 10: lock cells in input form

Hi,

how can I lock cells in an input form in BPC 10? My input sheet has three columns of data, current period, previous period and prior year, obviously only current period should be open for data enrty. Equally I would like to lock rows that contain summation accounts so that the values cannot be overriden. I use the EPMFormattingSheet but when I on that one I cannot define cell locking.

Thanks,

Arnold