Well I thought I had this entire problem figured out utilizing numerous nested IF statements however I quickly began to find holes in the solution and realize I need some help.

The setup is simple...I am tallying our print users pages printed totals on a monthly basis. Users are given 750 pages for free, pages 751 to 1500 are charged at $.03 and 1501+ are charged at $.05.

My original plan was along the following lines, where H2 is year to date total and I2 is the current month:
=IF(H2>1500,I2*0.05,(IF(H2 > 750,I2*0.03,(IF(I2 < 1500,IF(I2 >750, (I2-750)*0.03,0),((I2-1500)*0.05)+22.5)))))

I'm not sure how to account for those users that say have 50 pages in January then end up with 1800 in February, so that they get charged the $22.50 for those 751-1500 plus the approx $15 for next 300 pages. Thanks for any leads!