what is it's market value? why would someone spend 1600gp for it?
There is nothing to indicate that 1.) That the last part of the incantation is tied to the destination and 2.) that the destination can be changed.WOR is an example of a magical effect cast at one time/place then suspended until the trigger word is uttered at another time/place. Accordingly, it seems like the reader would specify the destination point when read with the caveat a successful spellcraft check might be required to recognize the original destination word needing changed.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.