如何为此特定目的创建excel VBA函数？

Question

我正在尝试为此目的创建功能：我有一年的出生名单，我想拿出当年的最后两个数字并将它们总和。如果这个总和小于10，那将是我需要的结果。如果结果大于10（例如：9 + 9 = 18），我将把这两个数字（1和8）分开并得到它们的总和（1 + 8 = 9。这小于10，所以它会是我的结果）

这是我的代码，但它只给我第一次拆分和求和的结果（本例中为18）：

Function test(yob as range) as integer
Dim sum, i, j, i2, j2 as integer

i = mid(yob, 3, 1)
j = right(yob, 1)
sum = i + j

If sum < 10 then
     test = sum
Else:
     i2 = left(sum, 1)
     j2 = right(sum, 1)

     test = i2 + j2
End If

End function

Answer 1

    Sub test()

        Debug.Print getSum(9, 9)
        '/ Prints 9
        Debug.Print getSumShort(7, 7)
        '/ Prints 5

    End Sub

    Public Function getSum(x As Long, y As Long)

        Dim res     As Long

        res = x + y

        Do While res > 10 '/ Keep repeating till its greater than 10
          res = (res \ 10) + (res Mod 10)
        Loop

        getSum = res

    End Function

'/ Another way using 9 as divider. 
Public Function getSumShort(x As Long, y As Long)

    Dim res     As Long

    res = (x + y) Mod 9
    getSum = IIf(res = 0, 9, res)

End Function

Answer 2

Function sum2d(year)
    sum2d=IIf(year mod 100, (year - 1) Mod 9 + 1, 0)
End Function

Sub Test
    For Each v in Array(1980, 2001, 2017)
        Debug.Print v; "=>"; sum2d(v)
    Next
Next