George. You can describe your loading coils to Nec by taking the
physical length of the coil, say, 1", and creating a number of wires
that divide into 1", say 5.
THen put a load on all 5 wires, the total load amount would be the sum
of the 5 loads.

This technique is used in one of my sample antenna files,
'mobile.ant' at:
www.nec2go.com

Regards Pat W0OPW