Nested IF formula help

Dears,
I need to prepare aging report. there are four ages i.e. 30,60,90 and 90+ days.
I want excel to check if the total PAST DUES was less than or equal to March billed amount, then it should be age (30), and if the sum of March and Feb billed amount was less than or equal Past dues then it should be in age 60, and if the sum of Feb, Jan and Dec are equal or less than Past dues then it should be age 90 and if the amount of Past dues was more than or equal to billed amount of March, Feb, Jan and Dec then it should be counted as 90+.
currently I'm able to make the formula in different cells but there will be some accounts in two or more than two ages. therefore need your support. thanks
Aging IF.PNG