amortisation schedule - really slow with formulas

Hi All,

I have built a prepayment amortisation calculator that works the following way...

The data is entered in the first columns of sheet "Council Rates" (Column A to Column M)
The calculation of prepayment amount then is worked out in the remaining columns to the right of that data for each entry
The data is then converted into a waterfall type table in "Council Rates Summary" tab for each month
The data is then consolidated into the final tab named "Data Summary"

Typically, there are at least 4 other expenses within the same workbook. All consolidated into their own waterfall summary, then all into the 1 data summary tab.

Wondering if anyone could have a look and advise any formulas that might be too detailed, or even put me in touch with a VBA guru to try to do it with macro's.
The idea being we can continually add additional expenses as they occur, and the amortization schedule is updated for the relevant period.

Thanks,
Jason