Converting absolute directories to relative paths when referring to external files - ms-access

Question

I'm designing a database that will incorporate many images so I've decided to link to external files by storing their paths and bounding an image control to that field. Here is the code that allows me to select the file and store it was a string:
Public Function ShowFileDialog() As String
Dim objFD As Object
Dim strOut As String
strOut = vbNullString
Set objFD = Application.FileDialog(msoFileDialogOpen)
If objFD.Show = -1 Then
strOut = objFD.SelectedItems(1)
End If
Set objFD = Nothing
ShowFileDialog = strOut
End Function
which is then called by a control button:
Private Sub Command128_Click()
Dim strChoice As String
strChoice = ShowFileDialog
If Len(strChoice) > 0 Then
Me.Path = strChoice
Else
'bleh
End If
End Sub
This stores the absolute directory of the selected file, however I recently realized that I need to store relative paths so that when the database and its associated directories are moved onto a new computer (which is very likely to happen) these links will be maintained.
UPDATE: The helpful tips provided by Hans Up enabled me to get this to work. Here is my revised and tidied up code.
Public Function GetPath()
Dim objFD As Object
Dim strOut As String
Dim strAbsolute As String
Dim strFolder As String
Dim strRelativePath As String
strOut = vbNullString
Set objFD = Application.FileDialog(msoFileDialogOpen)
If objFD.Show = -1 Then
strOut = objFD.SelectedItems(1)
End If
Set objFD = Nothing
strAbsolute = strOut
strFolder = CurrentProject.Path & "\"
strRelativePath = Mid(strAbsolute, Len(strFolder) + 1)
If Len(strRelativePath) > 0 Then
Me.Path = strRelativePath
Else
'bleh
End If
End Function
Private Sub Command128_Click()
GetPath
End Sub

Answer 1

Here is an Immediate window session which demonstrates techniques you can use to determine the relative path of your selected file ...
' folder where db file resides ...
? CurrentProject.Path
C:\share\Access
strFolder = CurrentProject.Path & Chr(92)
? strFolder
C:\share\Access\
' strChoice is the file path from your code sample;
' use Mid() to get the piece from that string which follows strFolder ...
strChoice = "C:\share\Access\image\foo.png"
strRelativePath = Mid(strChoice, Len(strFolder) + 1)
? strRelativePath
image\foo.png
' combine base folder and relative path again just to confirm we got the right pieces ...
? strFolder & strRelativePath
C:\share\Access\image\foo.png