If you have a given velocity but no given starting position, then position is the missing constant. If you measure some acceleration and time, you can integrate that into a delta-velocity, but not an absolute velocity.
You can measure your speed against the CMB as an "absolute velocity" (in your local observable universe), but for two locations that are a significant fraction of the width of the observable universe apart, "zero movement" relative to the CMB in each of those locations, will not be zero movement relative to each other, due to the expansion of space in between.
You can measure your speed against the CMB as an "absolute velocity" (in your local observable universe), but for two locations that are a significant fraction of the width of the observable universe apart, "zero movement" relative to the CMB in each of those locations, will not be zero movement relative to each other, due to the expansion of space in between.