I am still unsure what "1-numbered sheet" means, but in the workbook, it seemed to me that we are just wanting to delete sheets named simply with a four-digit (year) number. If my understanding is correct, maybe like:

In a Standard Module:
[vba]Option Explicit

Sub example()
Dim DIC As Object ' Scripting.Dictionary
Dim wks As Worksheet
Dim arrSheetNames As Variant
Dim n As Long
Dim NewestName As Variant
Dim sMsg As String

Set DIC = CreateObject("Scripting.Dictionary")

'// Check each worksheet's name, seeing if the trimmed (in case any errant //
'// leading/trailing spaces) name is a four-digit number. If true, trim the //
'// sheet's name for later, and add the name to our dictionary's keys (as //
'// a number, so we can use MAX later to find the newest). //
For Each wks In ThisWorkbook.Worksheets
If Trim(wks.Name) Like "####" Then
wks.Name = Trim(wks.Name)
DIC.Item(CLng(wks.Name)) = Empty
End If
Next

'// Just to make sure we have at least one sheet to worry about. //
If DIC.Count > 0 Then
'// Flip the keys into an array (presuming we are using the dictionary //
'// late-bound) and find the newest/greatest name. //
arrSheetNames = DIC.Keys
NewestName = Application.Max(arrSheetNames)
'// We have the newest name stored, so delete this from keys and re-write //
'// the array. //
DIC.Remove (NewestName)
arrSheetNames = DIC.Keys
'// Optional: Build a message to confirm with the user. //
sMsg = "Deleting:" & vbCrLf & vbCrLf
For n = LBound(arrSheetNames) To UBound(arrSheetNames)
sMsg = sMsg & vbTab & arrSheetNames(n) & vbCrLf
Next
sMsg = sMsg & vbCrLf & "Renaming: " & NewestName & " to: Calculator"

'// Rename latest sheet and loop through our array to delete the others. //
If MsgBox(sMsg, vbQuestion Or vbYesNo, "STOP! Okay to delete?") = vbYes Then
ThisWorkbook.Worksheets(CStr(NewestName)).Name = "Calculator"
Application.DisplayAlerts = False
For n = LBound(arrSheetNames) To UBound(arrSheetNames)
ThisWorkbook.Worksheets(CStr(arrSheetNames(n))).Delete
Next
Application.DisplayAlerts = True
End If
End If
End Sub[/vba]

Hope that helps,

Mark