DateDiff如果为null，则使用以前的时间

Question

我想在我的员工输入返回办公室的时间[AActReturn0]以显示在字段[AActDrive50]中时计算最终驾驶时间，但如果AActFinish5为空，我需要它转到AActFinsh4，但如果为空，则我需要它检查AActFinish 3，一直到AActFinesh1。我不确定我在这里做错了什么。我也试过Dim。我不知道该怎么做。

尝试#1:

Private Sub AActReturn0_AfterUpdate()
If AActFinish5 <> Null Then
AActDrive50 = DateDiff("n", [AActFinish5], [AActReturn0])
ElseIf [AActFinish5] = Null Then
AActDrive50 = DateDiff("n", [AActFinish4], [AActReturn0])
ElseIf [AActFinish4] = Null Then
AActDrive50 = DateDiff("n", [AActFinish3], [AActReturn0])

ElseIf [AActFinish3] = Null Then
AActDrive50 = DateDiff("n", [AActFinish2], [AActReturn0])
ElseIf [AActFinish2] = Null Then
AActDrive50 = DateDiff("n", [AActFinish1], [AActReturn0])
End If
End Sub

尝试#2：

Private Sub AActReturn0_AfterUpdate()
Dim Final As String
If AActFinish5 <> Null Then Final = AActFinish5
If Final = Null Then Final = AActFinish4
If Final = Null Then Final = AActFinish3
If Final = Null Then Final = AActFinish2
If Final = Null Then Final = AActFinish1
AActDrive50 = DateDiff("n", [Final], [AActReturn0])
End Sub

Answer 1

您可以使用Nz：

Private Sub AActReturn0_AfterUpdate()
Dim Final   As Date
Final = Nz(AActFinish5, Nz(AActFinish4, Nz(AActFinish3, Nz(AActFinish2, Nz(AActFinish1)))))
AActDrive50 = DateDiff("n", [Final], [AActReturn0])
End Sub