Bro...Ur calcium will not juz shoot up with the aid of CR.
As an example, for each 1 mEq/L alkalinity (2.8 dKH) the calcium reactor adds 20ppm calcium. If your tank starts out with 3 mEq/L alkalinity (8.4 dKH) and 320 ppm calcium, and you raise the alkalinity to 4 mEq (11.2 dKH) using the calcium reactor, then the calcium level will only increase to 340 ppm!
So dun worry abt ur calcium shootin up over the nxt 4days and hav a safe trip.
But u will nd to use an addictive [eg..increase calcium (reefez, seachem..)] to increase the Ca to the leve u wan and the CR will help u maintain the desired level.