Multiwfn forum

Hello,
    Something that I've been trying to do is compute the overlap between two molecules, each described by their own wavefunction. For example, if I have a water dimer, I would generate a wfn or fchk file for the first molecule, then do the same for the second. What I'd like to compute is the unperturbed overlap between the wavefunctions of these two molecules. I know that it is possible to compute overlap of molecular orbitals in dimers, but I have not seen a direct way to get the overlap of the total densities. Please let me know if this is a possibility with multiwfn.
Thank you,
Kevin