Code need to be expanded and running faster

Hi I have below code it change the format to text and the date like this DDMMYY. It works ok.
But if there is blanks or if I set the range so it cover after blanks, it run endless. If there is no blanks and the range is with date it run fast.
SO this is one of the problems, But also I need it to be expanded so it cover all these columns.
k2:K10000
N2:N10000
AR2:AR10000
And in top of that I need it to be able to do this in below sheets.
spain,italy,austria,portugal,france,belgium,netherlands
So I need to be changed for sure. And also the problem with the speed need to be fixed first.

Please have a look I have attached a sheet to work with.

P.s in the test sheet I did not change the sheet name to spain etc. but please do if you want to play with that.

Thanks in advance

Abjac

The code.

Sub DDMMYYSpain()
Dim ws As Worksheet
Dim rCell As Range
Dim rng As Range
Set ws = Sheets("spain")
ws.Select
Set rng = Application.Range("K2:K10000")
For Each rCell In rng
    rCell.NumberFormat = "@"
    rCell.Value = Format(rCell.Value, "DDMMYY")
Next rCell
End Sub