Disagg Issue

We use Prop Factors for disagg of Planner Adj KF (they input in % and uses a macro to apply that % against Stat Fcst), the disagg logic behind the KF is Average as its % Key figure. The problem is if the planner wants to apply a constant % for a group of products of which some of them have no Adj and some of them have some Adj. If he increases Adj there is no problem, if he gave –ve %, His total –ve Adj is going to the product which have % adj previously. How can we control this behavior any help is appreciated. Its not even considering the Prop factor for disagg in this scenario.