Understanding Yield: Does the Equation Need Breaking Down?

[Potaire]

Is this how it works? :

BE(product) - BE(reactant#1) - BE(reactant#2) => Yield from fusion of product

Easy enough, but what if reactant#1 and/or reactant#2 are also products of fusion?? Does the equation need to be broken down even further, or is the final BE for the final reactants all that is needed?

 

[Potaire]

This WAS a question---not sure if the above is correct.