confusion on the AVD on estate

Decedent passed away last October. Certainly looks like we will choose AVD for the value of the securities. But, what if we choose to sell some, but not all, of the securities before the 6 month date? The decedent owned shares in 7 companies. If we sell, we would sell all shares in a company at one time. Can we use the date of sale value for the shares sold before the 6 month period and choose the (April) date for the remaining shares? Thanks Harry