You are probably NOT going to be able to do it in this simplistic of a manner.
GoldMine will do one update (e.g. UFORECAST) and then the other (e.g. USIC). Well, after the first update, the data originally in that field (UFORECAST) is no longer available to be placed into the second field (USIC). At that precise moment in time, both fields hold the value that was originally in USIC.
A potential solution:
Have a 3rd "temporary field" available for the shuffling the data.
High level concept:
a. Copy UFORECAST to UTEMP.
b. Copy USIC to UFORECAST.
c. Copy UTEMP to USIC.
A POSSIBLE LOOKUP.INI approach:
NOTE: I have NOT invested the specific time to "test" this, so I may be missing a specific meticulous detail here. However, I hope you get the gist of what I'm suggesting?!?!? Clearly test very thoroughly and carefully.
Hope this feedback helps.
Thanks John. I figured I may need something like that. I will test it out and let you know.
I did some testing and it seems to work. I will fully test it out, but it appears to work.
I would also turn on log of history for changes, just in case.
John's solution is the correct solution to this question.
Turning on Log Changes in History, I don't believe, has any effect when the changes are made via the Lookup.ini.