EXCEL中日期改為顯示星期幾的自定義涵數(shù)

Function DateOfWeek(ByVal Yearf As Integer, ByVal Weekf As Integer, Optional ByVal Dayf As Integer = 1, Optional ByVal FirstDayOfWeek As Integer = 0)
    On Error GoTo ext
    Dim fd As Date, fw%
    fd = DateValue(Yearf & "-1-1")
    fw = Weekday(fd)
    FirstDayOfWeek = FirstDayOfWeek Mod 7
    DateOfWeek = fd + 7 * (Weekf - 1) + Dayf - IIf(Weekf = 1, 1, fw - FirstDayOfWeek)
    Exit Function
    ext://http://examda.com
    DateOfWeek = "#N/A"
    End Function