Child support arrears

My ex owes over $56,000.00 in back due child support & the judge is only willing to garnish his wages at the current support calculation of 28%. I know that the court can garnish up to 65% (no I'm not asking for them to increase it to this amount but to the original amount set in 1996, not the amount he got it lowered to in January because he falisly represented his income to the court - which has been pointed out to the court with nothing being done about it) of his disposable income since he does not support a 2nd family. When I mentioned this to the judge he said no only 28% in the state of Illinois. If someone knows of the law that states the amount can increase because of the obnoxious amount of arrears (& yes, I've been going back & forth to court over the past 15 years because of his unwillingness to pay) please let me know where I can find it so I can take it in with me to my next court date.