Assigning right values to the right row

Now I need a formula that does the following:

1. For entities with a value under the "Value" column, calculate the "Adjustment" (i.e., Target Value - Value).
2. For entities that are listed as counterparties, they get the adjustment of the Entity's row with inverse value. For example, if Entity 1 had an Adjustment of 10, and Entity 2 appears in the Counterparty column, Entity 2 would get assigned an adjustment of -10.

Also, the formula should allow for aggregation of several adjustments (for example, Entity 2 being counterparty twice for 2 different entities, so 2 Adjustments will be aggregated).

See example below. 

Thanks in advance!