統計某個日期區間內星期天的個數

Function SundayCount(StartDate As Date, EndDate As Date) As Long
    On Error GoTo Err_SundayCount:
    Dim Days As Integer    '區間天數
    Dim FirstSunday As Date    '第一個周日具體日期
    Dim NextSunday As Date    '下一個周日具體日期
    Dim Myweekday As Integer
    Dim i As Long
    Dim j As Long
    '確保日期都不為空，若為空則置為0
    If Not IsNull(StartDate) And Not IsNull(EndDate) Then
    '如果結束日期<開始日期，則為0
        If EndDate >= StartDate Then
            '如果天數大於7,則先確定第一個周日是哪個日期，再7天一加，直到大於結束日期
            Days = EndDate - StartDate
            ' If Days > 7 Then
            Myweekday = Weekday(StartDate)    '算出是周幾,星期天是1
            If Myweekday > 1 Then
                FirstSunday = StartDate + 8 - Myweekday
            Else
                FirstSunday = StartDate
            End If
            Debug.Print "最近的周日是: " & FirstSunday
            NextSunday = FirstSunday + 7
            i = 1
            SundayCount = 1
            For i = 1 To Days Step 7
                Debug.Print "下一個周日是: " & NextSunday
                If NextSunday > EndDate Then
                    If FirstSunday > EndDate Then
                        SundayCount = SundayCount - 1
                    End If
                    Debug.Print "周日數目是: " & SundayCount
                    Exit Function
                End If
                NextSunday = NextSunday + 7
                i = i + 1
                SundayCount = SundayCount + 1
                Debug.Print "周日數目是: " & SundayCount
            Next
        Else
            SundayCount = 0
        End If
    Else
        SundayCount = 0
    End If
Exit_SundayCount:
    Exit Function
Err_SundayCount:
    SundayCount = 0
    Resume Exit_SundayCount
End Function

Sub Test()
Debug.Print SundayCount(#2/6/2005#, #2/25/2005#)
End Sub