As time passes, keep in mind that some changes in the schedule are inevitable. Ideally, both parents should take part in any decisions relating to the residential schedule. Constant changes and/or significant changes based solely on the custodial parent's wishes, however, are neither legal nor reasonable. Frequent schedule variations are also not fair to the child, who must constantly try to adapt to the latest schedule.
If frequent 'hijacking' of the residential schedule is having an adverse effect on the child or your relationship with the child, retain an attorney and file a motion for contempt, citing interference with the residential schedule.