Sub test()
Dim cel As Range
Dim lRow As Long
lRow = Cells(Rows.Count, 1).End(xlUp).Row
For Each cel In Range("D2:D" & lRow)
If cel.MergeCells Then
cel.UnMerge
cel.Offset(1).Value = cel.Value
End If
Next
End Sub
Edit: If there's more than 2 rows merged. You'd probably want another step inside IF statement to store # of merged rows and loop on Offset().