I think you need to explain what you're wanting to do, functions just work like additional commands ie
function add(a,b)
return a+b
end function
if add(10,20) = 30 then print "10 + 20 = 30"
function add(a,b)
return a+b
end function
if add(10,20) = 30 then print "10 + 20 = 30"