There should be a provision in your parenting plan addressing this issue.
But, more pertinently, child custody orders in Missouri are based primarily, if not exclusively, on the best interests of the child. Assuming that your child is old enough and mature enough to voice his/her own opinions, if he/she does not want to visit a particular parent, that may carry the day. You can't force a child to do something he/she does not want to do.
If you would like to change the custody arrangement, you would have to file a Motion to Modify.
I am not your attorney. I do not represent you. This response is submitted for informational purposes only. This is not legal advice, nor is it intended to be taken as such. Anyone considering the above referenced situation should always consult an attorney within the jurisdiction before taking any action based on this, or any other information