VB中子程序或函数未定义怎么办啊？

Sub s2(i%)Dim a%, c(20) As String, sum%a = Len(Str(i))For j = 1 To ac(j) = Mid(Str(i), j, 1)sum = sum + Val(c(j))Next jIf sum = 10 ThenPrint iEnd IfEnd SubPrivate Sub Form_Click()Dim x%, y%, i%x = 100y = 999For i = x To yCall s2(i%)Next iEnd Sub