Locking Data into a cell
 

Is there a way to lock data into a cell? I have a formula that is pulling
items from another sheet(tab) and I want it to lock in the data pulled (if
possible by a certain date).
I have one master sheet and as items are imputted I want the the data
caputered on the last tab. However, I want the information added or deleted
to be only Caputered in a Row marked january - and then after Janyary the
information will be pulled into the Row marked Feb (etc).

any help?