Score one for the "I KNOW it's gotta be out there" determination gene! After multiple searches, I finally located a calculator program which allows you to:
1- save the list of figures with or without total
2- assign a name to the full calculation so you don't inadvertently overwrite it
3- reload whichever calculation list you want at another time
4- export PERFECTLY to MemoPad, i.e., column of figures with result if you got that far, or however far you got into the calculation list before being interrupted
Been using it daily for the past week without hassle, so I figure it's now safe to pass on the word.

Name: tApCalc
Platform: versions avail for Palm and PocketPC
Cost: $0
SPECIAL NOTES-- see below! <<< CRUCIAL!
URL: http://www.softtrends.com/PRODUCTS/tApCalc/tapcalc.html

=== Notes ===
There is no documentation in the tApCalcPRC.zip package, and I wasn't familiar with "AppForge's Booster", so I had to work through a few glitches before I could get this beauty to run as anticipated. Here's your cheat sheet to avoid irritations... Back up everything first via a HotSync, to be super safe! Trail & error = install in a certain order, one at a time.

1- First, go to http://www.appforge.com/booster.html and download the latest PalmOS version, which is #3. [PalmGear has v 2.1, which I could NOT get to work with this program.] If you have a previous version of Booster installed, remove it. Install Booster v3, then Hot Sync. BTW, the exe download version is in excess of a MB; look for the smaller prc/zip file instead:
. . . . . . . 30-410booster-palmos.zip. Contains one file: Booster.prc - 370,972 bytes
Dunno if it will work from an SD card, so I played it safe.

2- Next, grab the freebie calc file from above SoftTrends URL. Explode to get to the 2 contained prc files. Install as follows--
-- AppForge PalmPrint Fuser.prc, then HotSync
-- tApCalc-Install.prc, then HotSync.

When you're done, you'll notice there's a bit of a lag time between tapping the tApCalc program icon, and its appearance on screen. I have no clue why, but it's worth it. Add up a few figures to get the feel of the thing; if you want to retain the total, you'll have to end the calculation by hitting the equals key. Then, hit the menu key. Select Tape >> Save. Assign a name; be sure to change the radio button to "output"; then "done". Switch to MemoPad, and you'll see your calculations.

Above works without any hassles [Treo 90, PalmOS 4.1H, Launcher III 3.0.5, hacks installed: X-Master, Pop!, MagicText, McPhling, SelectDay]. If you detour from the suggested install procedure, be prepared for a tour of "Fatal Alert" city.
====

Initially, you may notice that after subsequent HotSyncs, parts of Booster are reinstalling itself [i.e., "Ingots", etc]. That weirdness disappears the next day, forever!