What is the test for applying to vary a custody order?

18. With these distinctions in mind, of marginal consequence though they may be, one approaches the decision in Gordon v. Goertz. That case dealt with an application to vary the provisions of an existing custody order and thus some time was devoted to the threshold question of the need to determine that there has been or would be a “change of circumstances” and what might constitute a change in the order of magnitude as to warrant a renewed inquiry into the best interests of the child. As there had been no previous order prior to this proceeding having been commenced we do not need to concern ourselves with much of the first part of the analysis.