Bug参数用错了一个，而且没有考虑指定天数可能是负数，Demo2来修正了：

Function FDemo(Dd As Date, Dnum As Integer) As Date
    Dim i, Md As Integer
    i = Int(Dnum / 5)
    Md = Weekday(Dd, vbMonday)
    If Md + Dnum < 5 and Md + Dnum > 0 Then
        FDemo = Dd + Dnum
    Else
        FDemo = Dd + Dnum + i * 2
    End If
End Function

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需求：自定义函数（日期，天数）结果是指定日期在指定工作日天数后的工作日期。要判断周六周日，不用考虑法定节假日。

Demo1

	

		Function FDemo(Dd As Date, Dnum As Integer) As Date
    Dim i, Md As Integer
    i = Int(Dnum / 5)
    Md = Weekday(Dd, vbMonday)
    If Md + Dnum < 5 Then
        FDemo = Dd + i'此处加i是错的，应该加Dnum
    Else
        FDemo = Dd + Dnum + i * 2
    End If
End Function 
	

简单测试了一下，能实现预期值，大家有空帮忙测试指正。