الاخوة الكرام 
ارجو شرح الكود التالي وبالاخص سطر 
If Nz(RC1(3), "") = "" Then
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    Dim SQL1, SX1 As String
    Dim RC1 As Recordset
    Set RC1 = CurrentDb.OpenRecordset("01_001_015", dbOpenDynaset)
    RC1.MoveFirst
    Do Until RC1.EOF
        If Nz(RC1(3), "") = "" Then
            RC1.Edit
            RC1(3) = SX1
            RC1.Update
        Else
            SX1 = RC1(3)
        End If
        RC1.MoveNext
    Loop
    RC1.Close
       'MsgBox "Done 1 / 50 "