Hope this starts you in the right direction
replace msaccess.exe with the name of your ms access 2003 name
Private Sub Access_Instances()
'citing source concept
http://msdn.microsoft.com/en-us/library/aa394372(VS.85).aspx
On Error Resume Next
Dim objWMIService As Object, colProcesses As Object, objProcess As Object,
objAccess As Object
Dim ProcessId As Long
Set objWMIService = GetObject("winmgmts:")
Set colProcesses = objWMIService.ExecQuery("Select * from Win32_Process
where name = 'msaccess.exe'")
For Each objProcess In colProcesses
ProcessId = objProcess.ProcessId
Debug.Print ProcessId & " " & objProcess.Caption
Set objAccess = objProcess
With objAccess
'reference access application object here
End With
Next
Set objAccess = Nothing
Set objProcess = Nothing
Set colProcesses = Nothing
Set objWMIService = Nothing
End Sub