VBA code for testing efficency
I know this isn't what you're asking, but what's up with your variables? You should always turn on Option Explicit which will catch things like k, q and i not being dimensioned.

When you don't define your variable, VBA defines it as a variant. I'm pretty sure variants are objects:


  Performance. A variable you declare with the Object type is flexible
  enough to contain a reference to any object. However, when you invoke
  a method or property on such a variable, you always incur late binding
  (at run time). To force early binding (at compile time) and better
  performance, declare the variable with a specific class name, or cast
  it to the specific data type.


So you pay a penalty when you don't dimension your variables.

I imagine defining your variables might shave some milliseconds off over the long run.



For variables I'm getting 570ish

For selection I'm getting 950ish

For i=1 to 10000 


using your variables is giving me about 5200 
while using option explicit I'm getting around 5100.


For i=1 to 50000


option explicit is 24165  
your variables is 24476


Option Explicit has the gainz.

And now, my version (why are you [A1].Selecting?) for i=1 to 50000 comes in at 23182. That right there should show you the .select statement was slowing it down.

Option Explicit

Private Declare Function GetTickCount Lib "kernel32.dll" () As Long

Sub UsingVaribles()
    Application.ScreenUpdating = False
    Dim NumberToday As Long
    NumberToday = 40000
    Dim StartTimer As Long
    StartTimer = GetTickCount
    Dim rngCells As Range
    Dim rng As Range
    Dim k As Long
    k = 1
    Dim i As Long
    Dim q As Long

    For q = 1 To 26
        For i = 1 To 50000
            NumberToday = NumberToday + 1
            Set rngCells = Cells(i, k)
            rngCells = NumberToday
        Next i
        Range(rngCells, Cells(1, k)).NumberFormat = "m/d/yyyy" ' 1 bug out
        k = k + 1
    Next q

    MsgBox (GetTickCount - StartTimer &amp; " Milliseconds")
    Application.ScreenUpdating = True
End Sub