Auto Save Shared Workbook and Update Display

This might get you started.

Paste in ThisWorkbook module

Private Sub Workbook_Open()
Application.OnTime Now + TimeValue("00:05:00"), "AutoSave"
End Sub

Paste in standard module

Sub AutoSave()
Application.DisplayAlerts = False
ThisWorkbook.Save
Application.DisplayAlerts = True

Application.OnTime Now + TimeValue("00:05:00"), "AutoSave"
End Sub