valeur max d'une celulle dans un classeur

Sub MaxClasseur()
    Dim i As Integer, lmax As Long
    lmax = 0
    For i = 1 To Worksheets.Count
        If Application.WorksheetFunction.Max(Worksheets(i).UsedRange) > lmax Then lmax = Application.WorksheetFunction.Max(Worksheets(i).UsedRange)
    Next i
    [A1] = lmax
End Sub

Function MaxOnglet(cell As Range) As Long
    MaxOnglet = Application.WorksheetFunction.Max(cell.Parent.UsedRange)
End Function

Option Explicit
Sub ChercheMaxA1()
Dim Sh As Worksheet
Dim Maximum As Double
Dim Feuille As String
    For Each Sh In Worksheets
        If Sh.Range("A1") > Maximum Then
            Maximum = Sh.Range("A1")
            Feuille = Sh.Name
        End If
    Next
    MsgBox Maximum & " est la plus grande valeur trouvée dans les cellules A1." & Chr(10) & _
    "Cette valeur se trouve dans la feuille " & Feuille & "."
End Sub

=MAX(Feuil1:Feuil3!A1)

Worksheets("Feuil1").Range("B1").FormulaLocal = "=MAX(" & Worksheets(1).Name & ":" & Worksheets(Worksheets.Count).Name & "!A1)"