hoe to use my NDR in a circuit

my NDR is.....

.subckt MolecularDiode pos neg

*the VCCS model has the problem of staying constant when the voltage is outside the data points
Gdiode pos negtest PWL(1) pos
+ neg 0,0 .08,100e-09 .16,200e-09 .25,300e-09 .32,400e-09 .4,500e-09 .52,600e-09 .55,700e-09
+ .65,800e-09 .7,700e-09 .75,200e-09 .78,100e-09 .8,0
+ .9, 0 1,0 1.2,0 1.5,0

Rtest negtest neg 0.1
.ends

Vs 1 0 dc 0.1v
X1 1 0 MolecularDiode

.dc Vs -2 2 0.025
.option post
.plot(I(X1.Rtest))
.end
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how can i use this model in a circuit and then simulate thiis circuit....
i am using hspice....
how can i use negative values of resistances in the NDR region of the resistance.....