Function lrqMonthInDay(ByVal dateYear As Integer, ByVal dateMonth As Integer) As Long
'dateYear:表示年份的数字；dateMonth：表示月份的数字
'示例：
    Me.控件名= lrqMonthInDay(dateYear,dateMonth)
    '本月第一天的日期
    Dim MonthOneDay As Date
    '下月第一天的日期
    Dim NextMonthOneDay As Date
If dateYear >= 1900 And dateMonth >= 1 Then
   '生成本月第一天的日期
    MonthOneDay = DateSerial(dateYear, dateMonth, 1)
   '生成下月第一天的日期
    NextMonthOneDay = DateSerial(dateYear, dateMonth + 1, 1)
   '计算结果以天“d”为单位,DateDiff的具体用法参考：
   'http://www.accessoft.com/article-show.asp?id=8866
    lrqMonthInDay = DateDiff("d", MonthOneDay, NextMonthOneDay)
Else
    MsgBox "变量不在允许范围内！请检查[年份]和[月份]。", 48, "输入错误"
End If
End Function

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