You have not yet made a (successful) edit. Your problem statement has not changed.
As to whether there is a substitute solution for using a CVX variable as an index, it depends on what you are trying to do. Perhaps there is a reformulation which complies with CVX’s rules. One possibility to handle certain non-convex constraints is use of binary or integer variables to achieve what you want, making use of CVX’s MIDCP capability. Given that you are using MOSEK, the MIDCP capability is available to you.