Excel 2007 macro

Private Sub Worksheet_Activate()
Dim mRng As Range, Cel As Range, c As Object
Dim firstaddress As String, k As Byte
Dim mNum As Integer, ur As Long, ritS As Long, rPre As Long
Range("E2:F31,L2:M31,S2:T31").ClearContents
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
Application.EnableEvents = False
Set mRng = Range("A2:A31,H2:H31,O2:O31")

ur = Sheets("Foglio1").Range("A" & Rows.Count).End(xlUp).Row
k = 0
For Each Cel In mRng
    mNum = Cel.Value
    With Worksheets("Foglio1").Range("C2:V" & ur)
        Set c = .Find(mNum, LookIn:=xlValues, lookat:=xlWhole)
        If Not c Is Nothing Then
            firstaddress = c.Address
            Do
                If k = 0 Then
                    Cells(Cel.Row, Cel.Column + 4) = c.Row - 2
                    k = 1
                    ritS = c.Row - 2
                    rPre = c.Row
                Else
                    If c.Row - rPre > ritS Then
                        ritS = c.Row - rPre
                    End If
                    rPre = c.Row
                End If
                Set c = .FindNext(c)
            Loop While Not c Is Nothing And c.Address <> firstaddress
            Cells(Cel.Row, Cel.Column + 5) = ritS
        End If
        
    End With
    k = 0
    ritS = 0
    rPre = 0
Next
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
Application.EnableEvents = True
MsgBox "Fine elaborazione"
End Sub