Hi Danny, give the attached plugin a try.

To install it, unzip it and copy the 2 files to the \commands sub-folder inside of MoI v2's main installation folder.

Then set up a keyboard shortcut and put in BisectorLine as the command name part of the shortcut.

Then when you push that key it should give you a quick way to build that in-between line. You can either preselect the 2 input lines to use before triggering it, or if you have a blank selection you can select 2 lines after triggering it as well.

Please let me know if you have any problems with it.

- Michael

EDIT: updated to fix repeat mode bug

EDIT: removed this version as it was not generating the correct kind of line, see this other message for an updated version:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3745.41