Putting number of days in proper month

I am trying to break apart the approved amounts into the proper months. I am not sure if I need to add extra columns for months after columns D&E or if there is logic to do.

Ulitmately I would like to run this across multiple columns for items over 200 days and put the information into the proper months.

Row 3 for example per the attached would be broken into the number of days for Aug'90, Sep'09, Oct'09....Aug'10.

Kinda fo new to writing logic information. I appreciate any help in regards to this. If columns need to be added or changes made please see the attached item and let me know.

Sincerely appreciate the help!