Perform ResultLookup() using dynamic dimension members

I am in the middle of a planning project and we have the requirement where we need to look up a value from another line item based on the dimension members of the current line item.

E.g

So for plant A, product A, operation 2 we want to look up the value at plant A, product A, operation 1. I know this can be done with attributes, however, it can be the case that operation 2 could have a different previous operation, so we can not hard code this, it needs to be dynamic. How can this be done in advanced calculations?