Mutual blocking - allow to block dates for a unit that is already blocked by a linked unit

If unit B and A are linked, and unit B is already blocked by a booking from Unit A, between eg 5-10th October, I am unable currently to do a manual block from 1st Oct - 31st Oct on unit B.

I would like to be able to block the full period to close off the unit for that period. If the booking in unit A is cancelled, as it stands currently, the dates in unit B will be automatically opened for sale, and I do not want them open.