My Partial calculator - give me feedback for improving this tool

[Pari Thiagasundaram]

I spent almost half a day on this excel sheet to play with partials. If i were to sell one, on the "Partials" sheet, i type in the numbers on anything that is highlighted in green (Except the one that says "DO NOT CHANGE THIS CELL". 

I can also look at the "Graph" tab to see how the partials look like. 

- Can any experienced note investors take a look at this and let me know if the excel sheet is right ? As I will be depending a lot on this file, i would appreciate if someone can give me a feedback.

https://www.dropbox.com/s/xnezovfk76mqwts/note-partials%20payment.xlsx?dl=0