Need to loop through all objects in an array to find the max value

I need to loop through a returned array of objects to find the max value within those objects. Is there an easy way to do this using nested loops? Can someone give me some clues on how to do that? I tried to create a nested workflow using a custom decision, but can't figure out how to define the parameters; what level, how do they pass in and out of the custom decision, etc. - thx