Private Sub Worksheet_Change(ByVal Target As Range)
Static MyArray() As Variant
Static idex As Long
If Target.Count > 1 Then Exit Sub
On Error GoTo ErrHandler

If Len(Trim(Range("A1"))) = 0 Then
If Target.Address <> "$A$1" Then
 If idex = 0 Then
  idex = 1
 Else
  idex = idex + 1
 End If
 MsgBox idex
 ReDim Preserve MyArray(1 To idex)
 MyArray(idex) = Target.Value
End If
ElseIf InStr(1, Range("A1"), "write", vbTextCompare) Then
 Application.EnableEvents = False
 Range("M1").Resize(idex).Value = _
   Application.Transpose(MyArray)
ElseIf InStr(1, Range("A1"), "clear", vbTextCompare) Then
 Columns("M").ClearContents
 Erase MyArray
 idex = 0
End If
ErrHandler:
Application.EnableEvents = True
End Sub

If you type "write" in A1 it writes the array in column M.  If you type
"clear" in A1, it clears the array.  If A1 is blank, it records the entry
made in the array.

If you want the array accessible from other procedures, then you need to
declare it as a public variable at the top of a general module
(insert=>module) along with idex and remove the declarations from the Change
event.