There seems to be no command for mutating a certain residue into a user defined amino acid. For instance, if I want residue 10 to be tryptophan, it seems I have to do this manually by selecting residue 10, bringing up the mutate option, and selecting tryptophan.

The only Lua command for mutate I could find is:
do_mutate([iterations])

The iterations make the mutate take longer, but the highest scoring identity is always selected. Is there a command with an amino acid parameter?

The reason I ask is I'd like to write a script to
1) mutate two nearby residues in all possible ways (20 X 20 = 400)
2) report their energies.

After this I want to
3) look at the top scores of this list and
4) know what pairwise mutations they correspond to.