Refering code to work on just one column

This code grabs the blank cells and pastes whatever above into it. Im needing it to do this just in column A.

Sub Fill_Blank_Cells()
 Selection.SpecialCells(xlCellTypeBlanks).Select
 Selection.FormulaR1C1 = "=R[-1]C"
 End Sub

This link shows what im trying to do!

http://www.extendoffice.com/document...lue-above.html

Thanks