Can I force my ex to work?

I have a joint custody and have the kids every other week. I only pay child support plus for someone to take care the kids while I am at work. The child support is enough for my ex to pay rent and live off the rest. So the ex did not made any effort to get a job. Which in the process will reduce my child support. Now that my youngest child starting school. Can I force my ex to get off the couch and find a job by a legal action.

No, you cannot force your ex to work. You can however seek a modification of support (3 years after entry of your most recent Order) and ask the court impute income to your ex. Imputing income to the other side will reduce your obligation moving forward.