MacMolPlt has the ability to automate the generation of a Linear Least Motion (LLM) path connecting two know structures. This path can be constructed in either cartesian coordinates or in Z-matrix style internal coordinates. LLM paths can be useful for locating a transition state, or at the very least, putting an upper bound on the height of a transition state. One problem with an LLM path using cartesian coordinates is that bonds may be overly stretched or compressed causing large variations in the energy. To avoid this problem you can use internal coordinates for the LLM path. Creating an LLM path in MacMolPlt is quite easy.
That's it. You will now find the requested number of structures in between the two structure you input. I recommend saving the LLM path at this point. You probably already have the energies for the two endpoints. However, you still need them for the points MacMolPlt created. To obtain these energies you will need to generate a series of input files to run single point energy calculations. You can generate these files by hand (by copying the coordinates of each frame out of MacMolPlt) or use MacMolPlt's Input Builder window to generate the input files for you (still one file at a time though). Once the calculations are done you can copy the desired energy information and use the Set Frame Energy... menu item to set the energy of each geometry. Once all points are input you can view the energy graph to see how the LLM path behaves.