I had found a few minutes, and whipped up the Excel macro for you:
Code:
Sub MyAutoFill()
Dim myLastRow
Dim myRow As Long
Application.ScreenUpdating = False
' Find last row with data in column D
myLastRow = Cells(Rows.Count, "D").End(xlUp).Row
' Loop through all rows starting on row 3
For myRow = 3 To myLastRow
If Cells(myRow, "C") = "" Then Cells(myRow, "C") = Cells(myRow - 1, "C")
If Cells(myRow, "F") = "" Then Cells(myRow, "F") = Cells(myRow - 1, "F")
Next myRow
Application.ScreenUpdating = True
End Sub
You can even call Excel macros from Access (see here: http://support.microsoft.com/kb/194611).