$Calc disallow subtraction and division?

So I have a snippet where $calc($5 %y)

I have it working fine.

BUT I want to not allow * or /

Any suggestions?

Why not paste the entire script?

Why not checking if * or / is in $5 or in %y?

Code:

if ($istok(* /,$5,32)) || ($istok(* /,%y,32)) echo -s * / used
else yourscript...