How do I calculate my share of child care expenses.

What do I use to calculate how much I need to pay toward my child's child care, medical benefits, other necessary expensive for my child. Her father and I are divorced and have equal custody. We don't pay each other any child support, but we each pay a percentage of her expenses based on our incomes. When we first calculated the amounts, we were both single. The expenses were split 46/54 based on our incomes at the time. We're trying to figure out what the new percentages should be, but everything says to use the AGI from our 2012 tax returns & he has since remarried & filed jointly. His AGI includes his new spouse's income. Is there some other info on the tax return or W2's that we can use to re-calculate? We have also both received raises over the past few years, so the amounts need to change.