Varying the order of diffraction in Plasmonic Wire Grating

Hi,
I am simulating in Comsol 4.2.I started simulating the PLASMONIC WIRE GRATING given in the model library.the simulation there is done by varying the angle of incidence.(in the parametric sweep angle of incidence is varied).

I want to modify this a little bit.So instead of angle of incidence i want to vary m(the diffraction order)

i have made the necessary changes .

In global variables i have taken the transmission angle beta_m=asin((m*lam0)/(d*nb)) which comes from m*lam0=d(nb*sin(beta_m)-na*sin(alpha)) here alpha=0 for normal incidence
na=R.I of air(upper domain of simulation)
nb=R.I of glass(lower domain of simulation)

The propagation vectors which i have defined are :

ka=emw.k0
kb=nb*emw.k0
kbmx=kb*sin(beta_m)
kbmy=kb*cos(beta_m)

The geometries and material properties have been defined as usual

In port1 i have taken the upper boundary ,wave excitation on and Eo=exp(-i*ka*x) and beta=abs(ka)

In port2 i have taken the lower boundary ,the Eo=-cos(beta_m)*exp(-i*kbmx*x)
and Eo= sin(beta_m)*exp(-i*kbmx*x) and beta=abs(kbmy)

Then i have added the periodic boundary condition as Floquet condition

In the parametric sweep i have varied m(-2,0.1,2)

But this gives me erroneous results!!
probably i am unable to vary /parametric sweep m.

Kindly help I want to find the transmiision for various m