My hubby and I are moving from Wyoming to Texas to be closer to his kids but we are scared his ex will move back to wy after we move down there. Is there anything that we can put in place so she can't move out of the state with out us oking it?

His kids are in Texas and his ex has primary physical custody? No, not unless there is something very unusual in the custody order providing that, if he moves to Texas, she cannot remove his chidren from there.