IF Date Monthly Cashflow

[ryancurran22]

I have a cash-flow which I need to calculate how much interest is paid each month to the day. The interest is built up over the first 6 month then the total accumulated is paid on the 7th Month then the interest is paid on a monthly basis thereafter. I am currently doing this by using an IF formula below -

=IF(MONTH(Cashflow Month)<(MONTH(Startdate+6),0,IF(MONTH(Cashflow Month)=(MONTH(Startdate)+6),Total interest so far,IF(Total interest so far <previous months total interest so far, This months interest,0)))

Cashlow Month is the month of which that cpum of cash-flow relates to
Startdate is the date the loan was borrowed from

This is how it is actually displayed


=IF(MONTH(V111)<(MONTH($J$6)+$L$2),0,IF(MONTH(V111)=(MONTH($J$6)+$L$2),V131,IF(V131<U131,(V127+V129),0)))

The formula works when it is within 1 calendar year however once it goes over to 2015 it doesn't pick up the dates correctly.

Can you help!?!?!?!