Yes, but you then need to use MANTIME commands to get the difference vector, and to compute the vector length time series.
It may be easiest to break the coordinate tuple into the components, e.g. for group1:
enter g1x atom x sele atoms1 end mass
enter g1y atom y sele atoms1 end mass
enter g1z atom z sele atoms1 end mass
That way, it's straightforward to compute r from sqrt(x**2 + y**2 + z**2) with MANTIME commands.