Handling .dll files

[spurs]

I am writing VBA code that has to interact with a .dll file named master.dll which will be located on a USB memory stick (for example possibly drive E: F: or G:. In each case the subdirectory where master.dll is located will be in a subdirectory called Tickets

So the .dll file can be
any drive letter X followed by
X:\Tickets\Master.dll

The excel file containing the VBA code can be run from a different drive than where the Master.dll resides

I realize that I need a statement something like:
Private Declare Function MasterRT Lib "X:\Tickets\Master.dll" (ByVal lpBuffer As String, ByVal nSize As Integer) As Integer

1) If I don't know the letter of the drive where the USB is plugged in; how should I code the above line?
2) How can I trap the error if Master.dll is not found or available ? If this is the case I want to properly shut down the macro.

 

[Jaafar Tribak]

Not sure if your dll will support aliases but try the following and see if it works for you :

Option Explicit

Private Declare Function C_MasterRT Lib "C:\Tickets\Master.dll" Alias "MasterRT" (ByVal lpBuffer As String, ByVal nSize As Integer) As Integer
Private Declare Function D_MasterRT Lib "D:\Tickets\Master.dll" Alias "MasterRT" (ByVal lpBuffer As String, ByVal nSize As Integer) As Integer
Private Declare Function E_MasterRT Lib "E:\Tickets\Master.dll" Alias "MasterRT" (ByVal lpBuffer As String, ByVal nSize As Integer) As Integer
Private Declare Function F_MasterRT Lib "F:\Tickets\Master.dll" Alias "MasterRT" (ByVal lpBuffer As String, ByVal nSize As Integer) As Integer
Private Declare Function G_MasterRT Lib "G:\Tickets\Master.dll" Alias "MasterRT" (ByVal lpBuffer As String, ByVal nSize As Integer) As Integer


Sub Test()

    Dim oFSO As Object, oDrv As Object, lPathLength As Long
    Dim lErrNumer As Long, sErrDescription As String
    Dim lpBuffer As String, nSize As Integer
    
    lpBuffer = "Hello":       nSize = 5
    
    Set oFSO = CreateObject("Scripting.FileSystemObject")

    For Each oDrv In oFSO.Drives
    
        On Error Resume Next
        lPathLength = Len(Dir(oDrv.DriveLetter & ":\Tickets\Master.dll"))
        
        If lPathLength Then
            Select Case oDrv.DriveLetter
                Case "C"
                    Debug.Print C_MasterRT(lpBuffer, nSize)
                Case "D"
                    Debug.Print D_MasterRT(lpBuffer, nSize)
                Case "E"
                    Debug.Print E_MasterRT(lpBuffer, nSize)
                Case "F"
                    Debug.Print F_MasterRT(lpBuffer, nSize)
                Case "G"
                    Debug.Print G_MasterRT(lpBuffer, nSize)
            End Select
            Exit For
        End If
        
    Next oDrv
    
    lErrNumer = Err.Number
    sErrDescription = Err.Description
    If lErrNumer Then
        On Error GoTo 0
        Err.Raise lErrNumer, , sErrDescription
    End If

End Sub

 

[spurs]

This works fine
Thank you !