How to track highest stock price across sessions

 You need code for this. However, what kind of code you need depends upon how you udate yoiur stock quotes. Here is a system where the update is done automatically.  If you update the quotes manually a much simpler method can be used.

This ethod is demonstrated in the attached workbook. This is the code it contains. Observe that it must be in the code sheet belonging to the worksheet on which you want the action. That is a module created by Excel, not one you inserted yourself. In the attached workbook it's the module of the worksheet TXL_5418.

Private Sub Worksheet_Change(ByVal Target As Range)
    ' 240

    Const TriggerClm    As String = "A"     ' change to suit
    Const RecordClm     As String = "C"     ' change to suit

    Dim TriggerRng      As Range            ' defining rows in TriggerClm
    Dim Trigger         As Variant          ' the changed value

    ' react to changes from row 2 to the row below the last used row
    Set TriggerRng = Range(Cells(2, TriggerClm), _
                           Cells(Rows.Count, TriggerClm).End(xlUp).Offset(1))
    With Target
        ' don't react if several cells were changed simultaneously
        If .Cells.CountLarge = 1 Then
            Trigger = .Value
            With Cells(.Row, RecordClm)
                If Val(Trigger) > Val(.Value) Then
                    ' prevent the change from calling this procedure
                    Application.EnableEvents = False
                    .Value = Trigger
                    Application.EnableEvents = True
                End If
            End With
        End If
    End With
End Sub

Please take the time to read the comments I inserted in the code.