Running the slider before next iteration

I am working on this project where I use an external plugin, which does not understand multibranch tree structure. This have forced me to separate the tree using the index-slider. The data from each branch is then calculated and recorded using the data recorder. In order to calculate a fitness value I need all the data streams to be calculated one by one (for every integer in the index-slider). Once the fitness value is found Galapagos should continue with the next iteration and optimize my solution.

Is there a way to make sure that every index in the slider is calculated before Galapagos is doing its thing?

I should mention that the stuff inside the cluster "components and clusters" is rather heavy, takes a few seconds for every index.

Hope anyone have experience with similar situations, any help is highly appreciated!