I am sure this exists here already, have a look at lee-mac.com he may have something, google I am positive I have seen this recently. It just asks for vertice points and fillets as it goes. Will try to find for you.
OK Fillet Polyline, R, enter radius, pick pline its filleted, then offset, erase original pline.
Found some time just pick pline points then press enter.
pline by pick pts offset with rad.lsp
GETVALS3.lsp