我正在使用嵌套If语句和For Next语句来检索和更改表中的数据

Question

出于某种原因，一周中的每一天都填充有“定时”。我正在测试一个空值，但似乎在表中没有看到任何值

我正在使用DLookup来测试该值是否正确，似乎工作正常。

Dim i As Integer
Dim j As Integer
Dim db As DAO.Database
Dim wc As DAO.Recordset
Dim stc As DAO.Recordset
Set db = CurrentDb
Set wc = db.OpenRecordset("Weekly_Challenges")
Set stc = db.OpenRecordset("Weekly_StartTime_Challenges")

amRoutine = DLookup("AMRoutineStartTime", "Standard_Actions", "UserId=" & Me.UserID.Value & " And WeekNumber=" & Me.WeekNumber)

If Form_Weekly_Challenges_subform.StandardAction.Value = "AM Routine" Then
    If amRoutine = -1 Then
        For i = 0 To stc.RecordCount - 1
        If stc.Fields("StartTimeAction") = "AM Routine" Then
            For j = 0 To wc.RecordCount - 1
                If wc.Fields("StandardAction") = "AM Routine" Then
                    If stc.Fields("Monday") = Null Then
                    wc.Edit
                    wc.Fields("Monday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Monday") = "Timed"
                    wc.Update
                    End If
                    If stc.Fields("Tuesday") = Null Then
                    wc.Edit
                    wc.Fields("Tuesday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Tuesday") = "Timed"
                    wc.Update
                    End If
                    If stc.Fields("Wednesday") = Null Then
                    wc.Edit
                    wc.Fields("Wednesday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Wednesday") = "Timed"
                    wc.Update
                    End If
                    If stc.Fields("Thursday") = Null Then
                    wc.Edit
                    wc.Fields("Thursday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Thursday") = "Timed"
                    wc.Update
                    End If
                    If stc.Fields("Friday") = Null Then
                    wc.Edit
                    wc.Fields("Friday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Friday") = "Timed"
                    wc.Update
                    End If
                    If stc.Fields("Saturday") = Null Then
                    wc.Edit
                    wc.Fields("Saturday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Saturday") = "Timed"
                    wc.Update
                    End If
                    If stc.Fields("Sunday") = Null Then
                    wc.Edit
                    wc.Fields("Sunday") = ""
                    wc.Update
                    Else
                    wc.Edit
                    wc.Fields("Sunday") = "Timed"
                    wc.Update
                    End If
                End If
            wc.MoveNext
            Next j
        End If
        stc.MoveNext
        Next i
        End If
     Else
End If

星期一，星期三和星期五应设置为“定时”，其余应为空