You need to take your copy of your divorce decree and have it reviewed by an experienced family law attoreny. The decree is the first place to start in determining your rights and abilities.
Then we need to look at the actual facts: You say "kids", plural; so are you visiting the other children? When is the dance, and how long does it last? Did your ex give you any notice of the dance? What kind of dance is it?
Depending on the answers to these questions, your ex may be acting wrongfully and you might be able to seek a finding of contempt against her, and maybe obtain makeup visitation. If you go down this road, you might even be able to recapture the costs for the additional travel involved in a makeup visit.
You really should review all of this with an experienced family law attorney. I could assist you, if you so desire.
David R. Hartwig
801-486-1715
Answered on Apr 08th, 2016 at 8:18 AM