Setting dielectric constant in CST

For example, metal(silver,gold) has dielectric constant, epsilon of
negative ε1 and low positive ε2 in optical frequency.
( ε=ε1+iε2,ε1=n2-k2,ε2=2nk where n is refractive index,k is extinction coefficient)
So I want to set the dielctric constant of negative. Do you know the methods?
Software is CST microwave Suite 2006.
Thank you.

hello,
I have tried this before, I tried to use the dispersion model in CST to set the material to have negative er at certain frequency (since er cannot be negative over all the frequency spectrum). but it didn't work

Hi,
Metal at optical frequencies generally behaves like a "drude Material" If you check the help file for this material type you can find the relation between the drude parameter (plasma frequency, collision frequency..) and eps1 and eps2. If you have eps1 and eps2 you can easily fit the corresponding drude parameter.
I have done this before
If you check the material dispersion plot you will see that eps1 is indeed negative as desired.
F.

you can check the macro for the drude model u need to know dielectric constant or n and k.
I think it will work
cheers