You can use program 3drotate with the -1Dfile option to read in motion parameters from the -1Dfile output from 3dvolreg and apply them to another dataset. You need to be aware that if the second dataset is of a different size than the first, then the results may not be right, since rotations are always about the center of the volume, and if the volumes have different sizes, then they may have different centers. But if all 3 volumes have the same 3D grids, then you should be able to try the method you've outlined.
Zorkon the Volregimonious