If you lock the period (e.g. Tuesday Pd 3 or whatever) then the block will retain "ownership" of the period if you unbuild the block, but this doesn't lock the contents. You llock the contents of the period in the same way (i.e. by right-clicking etc.) so that they also go green (if hard lock). Unbuilding the block will then keep the contents of this period too.
On the other hand, I might have misunderstood the problem...
Glenn