Take the Colorado child support formula woroksheet (I'm sureu AnswerGuy can point you to the website faster than I can). Add what you think is his new incomeinto it and find out if there's at least a 15% difference in the support. Then get the paperwork online to go ahead & file for a modification of support in Colorado. You can pretty much do it all online or by phone, but if the court decides to hold a hearing on the issue (if he contests the change), then you will want to be there on that day because the judge will find it harder to do wrong by you if your face is in front of him or her in the courtroom.

In the process, your ex will have to prove his current income. If you have guessed wrong, then the amount it changes might not be what you think... but heck, if you have guessed LOW, it's quite possible that the true income he's getting now will really make the support amount higher than what you think it shoudl be and he'd be crazy to contest it...

But step one is to get the formula and put the numbers you think are current into the current formula just to see what pops up.. .if there's no 15% difference in the bottom line of support (not 15% change in his income, but 15% change in the support), it's not worth bothering to try to get a change. After a decade, most support amounts will change by that much, so you'll probably be pleasantly surprised...

Figure out how much of a change is likely, and you ight find it would be worth hiring an attorney to get it done right...