Your attachment isn't working. However, what I will say is that you need to have a cell for each month that is the initial loan amount minus any payments up to that month. You would use that adjusting value in your PPMT and IPMT fields as the PV. So, let's say the initial loan is for 1000, and then in the 3rd month there is an extra 30 principal payment. You would have this:
Month PV
1 1000
2 1000
3 970
4 970
etc.

Curious, is this how it is handled in China? In the US, the payments usually stay the same and the loan's end date is adjusted when extra principal payments are made.