herhangi bir dll'i visual basic 6 ile çağırmak için biraz hamallık yapmak gerekir, aynı zamanda çağırılacak DLL içindeki fonksiyon ve metodların ve isimlerinin de bilinmesi gerekir. Yani haydi al bu DLL'i kullan dersen o da sana Runtime Error diye cevap verir..

Option Explicit

' Windows API method declarations
Private Declare Function FreeLibrary Lib "kernel32" (ByVal hLibModule As Long) As Long
Private Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
Private Declare Function GetProcAddress Lib "kernel32" (ByVal hModule As Long, ByVal lpProcName As String) As Long
Private Declare Function CallWindowProc Lib "user32" Alias _
    "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, _
    ByVal Msg As Any, ByVal wParam As Any, ByVal lParam As Any) _
    As Long

Private Declare Function FormatMessage Lib "kernel32" Alias _
    "FormatMessageA" (ByVal dwFlags As Long, lpSource As Long, _
    ByVal dwMessageId As Long, ByVal dwLanguageId As Long, _
    ByVal lpBuffer As String, ByVal nSize As Long, Arguments As Any) _
    As Long

Const FORMAT_MESSAGE_FROM_SYSTEM = &H1000

Const MyFunc As String = "MYFUNC"
Const MyDll As String = "mylib.dll"

Sub Main()

    ' Locate and load the DLL. This will run the DllMain method, if present
    Dim dllHandle As Long
    dllHandle = LoadLibrary(MyDll)

    If dllHandle = 0 Then
        MsgBox "Error loading DLL" & vbCrLf & ErrorText(Err.LastDllError)
        Exit Sub
    End If

    ' Find the procedure you want to call
    Dim procAddress As Long
    procAddress = GetProcAddress(dllHandle, MyFunc)

    If procAddress = 0 Then
        MsgBox "Error getting procedure address" & vbCrLf & ErrorText(Err.LastDllError)
        Exit Sub
    End If

    ' Finally, call the procedure
    CallWindowProc procAddress, 0&, "Dummy message", ByVal 0&, ByVal 0&

End Sub

kodu kendim yazmadım, kopyalayapıştırspordur fakat isimleri düzenlediğinde çalışır.

Bu arada; metodlarını bilmediğim DLL'ler ile ilgili bilgi almak için Delphi kullanırım Import Component=>Type Library