Firstly the AutoFill destination range starts on the same range as the cell
that holds the first value. In this case A4. Following should do the trick.

Range("A4").Select
Selection.AutoFill Destination:=Range("A4:NETDAYS")

However, it is not necessary to actually select. The following code is the
better method.

Range("A4").AutoFill Destination:=Range("A4:NETDAYS")


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Regards,

OssieMac