Macro To Fill Blank Cells

I wonder if soeone could change the following macro so that the bottomcell
is set to be as far down as there is content in Column "A". As it stands if I fill in blank cells in Column "C" and the last cell with data is say C10 it does just this. But if the actual last row with data in column "A" is A14 then cells C11, C12, C13, and C14 are ignored. C11, C12, C13, and C14 should be the same as C10 above them.

Sub FillBlankCells()
Dim topcell As Range, bottomcell As Range
Set topcell = Cells(1, ActiveCell.Column)
Set bottomcell = Cells(16384, ActiveCell.Column)
If IsEmpty(topcell) Then Set topcell = topcell.End(xlDown)
If IsEmpty(bottomcell) Then Set bottomcell = bottomcell.End(xlUp).Offset
Range(topcell, bottomcell).Select
Selection.SpecialCells(xlBlanks).Select
Selection.FormulaR1C1 = "=R[-1]C"
End Sub

Other macros recognize the actual last row.... but have issues with columns formatted as Text. The macro above doesn't create problems with columns formatted as "Text".