vb怎样编写求和∑程序？

Question

要求输入如图所示的f(k),a,b接着就能算出结果

Answer 1

private function msum(a as integer,b as integer)
s=0
for k=a to b
s=s+f(k)
next
msum=s
end function
private function f(k as integer)
... '提问未给出f(k)的具体算式，这里以省略号代替
end function