Amortize specific period ranges

[Dave Britten]

I just refinanced our house, and in the process, discovered a financial feature I really like: being able to amortize a specific, arbitrary (but contiguous) range of periods.

For example, we've made 73 payments on the old loan. I can just punch in 1 to 73 (the actual input method differs by calculator), and amort those payments, giving me total interest and principal paid so far, as well as remaining balance. Pretty much every financial can do that part.

But if I want to amort the remaining portion of the loan, not all calculators will let you enter 74 - 360, and amort those. Often you have to amort the first 73 payments, subtract 73 from the total number of payments, then amort that many remaining payments. Not a HUGE deal, but extra steps that are a bit annoying when doing a bunch of what-ifs and playing with numbers.

These are the models I found that let you punch in any range of payments and amort those, optionally advancing to the next set of an equal number of periods. What else can do it? I'm interested in any of the inferior non-HP brands too.

10B
10BII
10BII+
TI BAII Plus (I really like the feature set, but the keyboard misses keystrokes with fast typing, and it's really light and has no rubber feet. You have to chase the damn thing all over your desk.)
TI BAII Plus Professional
Sharp EL-533 (Pretty slow amorts on this one, but it's so delightfully petite.)

Also, I'm sure I could program it on the 41C easily enough, but considering it's pretty slow at amorts, I could compute this kind of stuff manually much faster on, say, a 10BII+.

A further annoyance on the 12C and 14B is that they also update the values stored in n and PV to represent the total periods amortized so far and the remaining balance respectively.

Can this be implemented easily with a 17BII solver equation? I don't see any amort functions mentioned in the manual, and I don't think you can directly reference the values stored in the TVM variables.