Detailed mortgage overpayment calculator

[dollahsains]

Can anyone recommend a detailed mortgage overpayment calculator that allows changing the interest rates midway, and overpayments at a specific date? Or at least the latter?
None of the ones I've looked at (MSE etc) allow me to specify the date of the overpayment. Or at least, a specified period of time (year/month/whatever) from the current point.
Thanks

I’ve used quite a few calculators and not come across that.
Can you not just use the MSE calculator twice? Take the remaining balance after your first calculation, then use it as the start point to enter with the changed interest rate / overpayment value?

The downloadable mortgage spreadsheet from The Humble Penny is really good, not sure it has exactly what you’re looking for but is the best I’ve used

https://thehumblepenny.com/