Let's say that my tool enables you to create remote usability test (kind of). Users need a new feature - task randomization. When user design a project, he/she can add a survey but it isn't obligatory.

If user chooses 'Task randomization' - ON, he/she should somehow tie up a task with a matching survey to avoid a situation when project flow will look like this:

Welcome page -> Task 3 -> Survey 1 -> Task 2 -> Survey 3 -> Task 1 -> Survey 3 -> End

Do you have any idea how to design such interaction?