You can use ShellExecute to open a file:

http://www.mvps.org/access/api/api0018.htm

But I'll do you 1 better. MapPoint is a Microsoft Office VBA client. Here's
some code that will open a map inside an Access form and plot a map with
directions between 2 addresses. The map is displayed in a Bound Object frame
(objMap):

Private Sub cmdMap_Click()
Dim oApp As Object
Dim oMap As Object
Dim oPush(1 To 2) As Object
Dim oLoc(1 To 2) As Object

Set oApp = CreateObject("Mappoint.Application")
Set oMap = oApp.NewMap
Set oLoc(1) = oMap.Find(Address & " , " & City & " , " & State)
Set oLoc(2) = oMap.Find(Address2 & " , " & City2 & " , " & State2)

   If Not oLoc(1) Is Nothing Then
       Set oPush(1) = oMap.AddPushpin(oLoc(1))
       oPush(1).GoTo

       If Not IsNull(MyName) Then oPush(1).Name = MyName
       oPush(1).Highlight = True

       If Not oLoc(2) Is Nothing Then
           Set oPush(2) = oMap.AddPushpin(oLoc(2))

           oPush(2).Highlight = True

           With oMap.ActiveRoute
               .Waypoints.Add oLoc(1)
               .Waypoints.Add oLoc(2)
               .Calculate
           End With
           oMap.CopyDirections
           DoEvents
           Me.txtDir.SetFocus
           DoCmd.RunCommand acCmdPaste
       Else
           txtDir.SetFocus
           txtDir.Text = "No second location found!"
       End If

       oMap.DataSets(1).ZoomTo
       oMap.CopyMap
       objMap.Visible = True
       objMap.Action = acOLEPaste

       lblMapInfo.Caption = ""
   Else
       lblMapInfo.Caption = "Address Not Found!"
   End If
   Set oMap = Nothing
   Set oApp = Nothing
   Me.SetFocus
End Sub