Crystal Reports Date Formula

Message

   I need to display in a report due dates of invoices. The formula that I need is to use a date, add 45,60, or 90 days, and the due date is the end of that month (after adding the days.) For example, 60 days from Nov 24 is January 24, so the due date that should be returned by the formula is January 31. 

Another term that needs to be accounted for is adding 90 days to the date, and the due date will be the next 10th of the next month. For example, date is November 24, adding 90 days gets February 24, so the due date would be March 10. 

Thanks in advance for any help! 