Running Macro After A Specified Time

I have a macro that would run once the workbook is opened. This macro would then open another excel file to get updates then close it. Now this file is also being accessed by other persons in the network but just for a split second. Since an opened file would result into an error, what proper codes should I add so that if the file is currently in use, the macro would then run again after 5 seconds and would do the same thing until the file is ready? This is what I have so far. All in the standard module.

Sub Updater()
Dim updatePath As String
updatePath = Worksheets("Entries"). Range("E104")
Application. ScreenUpdating = False
Workbooks.Open (updatePath)
On Error Goto Errorhandler
Workbooks("APTupdater.xls").Close True
Application.ScreenUpdating = True
Exit Sub

Errorhandler:................