can you help me about this code

[okanerkaymaz]

Hi, friends

CODE:
/* this is part of specification of biological properties */

Area = 100 // um2
Nasingle=0
Ksingle=0

objref u,f
func gauss(){
m=0 s=1
u = new Random()
geu=u.uniform(0,1)

z=s*sqrt(2*log(1/(1-geu)))
feu=u.repick()
x=m+z*sin(2*PI*feu)
return x
}
// argument should be desired area in um2

func varyansm() {
varm=(2/Nasingle)*(ChannelBuild[0].aliases.am*ChannelBuild[0].aliases.bm)/(ChannelBuild[0].aliases.am+ChannelBuild[0].aliases.bm)

return varm

}

func varyansh() {
varh=(2/Nasingle)*(ChannelBuild[0].aliases.ah*ChannelBuild[0].aliases.bh)/(ChannelBuild[0].aliases.ah+ChannelBuild[0].aliases.bh)

return varh

}

func varyansn() {
varn=(2/Ksingle)*(ChannelBuild[1].aliases.an*ChannelBuild[1].aliases.bn)/(ChannelBuild[1].aliases.an+ChannelBuild[1].aliases.bn)

return varn
}

vma=varyansm()
vh=varyansh()
vn=varyansn()

proc noise(){
gu=gauss()
gm=sqrt(vma)*gu
ChannelBuild[0].aliases.m'=ChannelBuild[0].aliases.m'+gm
gh=sqrt(vh)*gu
ChannelBuild[0].aliases.h'=ChannelBuild[0].aliases.h'+gh
gn=sqrt(vn)*gu
ChannelBuild[1].aliases.n'=ChannelBuild[1].aliases.n'+gn
}
I wan to add gm,gh,gm values in each t times in m',h',n' and i writed a hoc file with above codes but
i take error messages wich is "nrniv: division by zero
in foxlu.hoc near line 40
vma=varyansm()
^
varyansm( )
xopen("foxlu.hoc" )
NEURONMainMenu[0].execute1("{xopen("foxlu.hoc")}" )
NEURONMainMenu[0].load_file(0"./foxlu.hoc" , )
and others"
how can i do different any way?

i known .mod file
i must wirte mod file
but i don't know how it will be writen
can anyone write a example for me