Private Sub cmd_open_1_Click()
Dim Foldername As String
    Foldername = "D:\PDF"
    Shell "C:\WINDOWS\explorer.exe """ & Foldername & "", vbNormalFocus
End Sub

Private Sub cmd_open_2_Click()
Dim Foldername As String
    Foldername = "D:\PDF\about.jpg"
    Shell "C:\WINDOWS\explorer.exe """ & Foldername & "", vbNormalFocus
End Sub

Private Sub cmd_open_Click()
Dim Foldername As String
Dim t1 As String
Dim t2 As String
    Foldername = Me.pdf_link_document
    t1 = InStr(1, Foldername, "#")
    t2 = Left(Foldername, t1 - 1)
    Shell "C:\WINDOWS\explorer.exe /select,""" & t2 & "", vbNormalFocus
End Sub