In some circumstances, you use the CreateObject function to create an object from an ActiveX class. The CreateObject function receives the class name as argument, and creates the object for you. In order to create the object, it loads and uses the right library or executable file that contains the interface for that object.
For Example:
set objApplication = CreateObject("Word.Application")

When you run the above code, the CreateObject will use the winword.exe in order to interact with the objects of Microsoft Word.
The following code snippet shows how to reveal the filename that will be used for a specific ActiveX class. It does it by reading the class definitions from the Registry.

Private Declare Function RegOpenKeyEx Lib "advapi32.dll" Alias "RegOpenKeyExA" _ (ByVal hKey As Long, ByVal lpSubKey As String, ByVal ulOptions As Long, ByVal samDesired As Long, phkResult As Long) As Long Private Declare Function RegCloseKey Lib "advapi32.dll" _ (ByVal hKey As Long) As Long Private Declare Function RegQueryValueEx Lib "advapi32.dll" Alias "RegQueryValueExA" _ (ByVal hKey As Long, ByVal lpValueName As String, ByVal lpReserved As Long, lpType As Long, lpData As Any, lpcbData As Long) As Long Private Const HKEY_CLASSES_ROOT = &H80000000 Private Const SYNCHRONIZE = &H100000 Private Const KEY_NOTIFY = &H10 Private Const KEY_ENUMERATE_SUB_KEYS = &H8 Private Const KEY_QUERY_VALUE = &H1 Private Const STANDARD_RIGHTS_ALL = &H1F0000 Private Const READ_CONTROL = &H20000 Private Const STANDARD_RIGHTS_READ = (READ_CONTROL) Private Const KEY_READ = ((STANDARD_RIGHTS_READ Or KEY_QUERY_VALUE Or KEY_ENUMERATE_SUB_KEYS Or KEY_NOTIFY) And (Not SYNCHRONIZE)) Private Const ERROR_SUCCESS = 0& Private Const REG_SZ = 1 ' Unicode nul terminated string Private Const BUFFER_SIZE = 1024 'The following function truncate the null character from a string. Private Function TrimZero(str As String) As String Dim lngPos As Long lngPos = InStr(str, Chr$(0)) If lngPos > 0 Then TrimZero = Mid$(str, 1, lngPos - 1) Else TrimZero = str End If End Function Private Sub GetFilenameFromClass(strActiveXClass As String) Dim hKeyCLSID As Long Dim hKeyClassFile As Long Dim strCLSID As String Dim strBuffer As String * BUFFER_SIZE Dim blnError As Boolean Dim blnFound As Boolean 'Find the class name in the Registry, under the HKEY_CLASSES_ROOT branch. If RegOpenKeyEx(HKEY_CLASSES_ROOT, strActiveXClass & "\CLSID", 0, KEY_READ, hKeyCLSID) = ERROR_SUCCESS Then 'If we find the right key, read the CLSID value. If RegQueryValueEx(hKeyCLSID, "", 0, REG_SZ, ByVal strBuffer, BUFFER_SIZE) = ERROR_SUCCESS Then strCLSID = TrimZero(strBuffer) 'find the key containing the class filename: If RegOpenKeyEx(HKEY_CLASSES_ROOT, "CLSID\" & strCLSID & "\InprocServer32", 0, KEY_READ, hKeyClassFile) = ERROR_SUCCESS Then blnFound = True ElseIf RegOpenKeyEx(HKEY_CLASSES_ROOT, "CLSID\" & strCLSID & "\LocalServer32", 0, KEY_READ, hKeyClassFile) = ERROR_SUCCESS Then blnFound = True End If If blnFound Then 'If we find the right key, read the value: If RegQueryValueEx(hKeyClassFile, "", 0, REG_SZ, ByVal strBuffer, BUFFER_SIZE) = ERROR_SUCCESS Then MsgBox "The class filename is " & TrimZero(strBuffer) Else blnError = True End If 'Close the key handle RegCloseKey hKeyClassFile Else blnError = True End If Else blnError = True End If 'Close the key handle RegCloseKey hKeyCLSID Else blnError = True End If If blnError Then MsgBox "The " & strActiveXClass & " class doesn't exist in your registry", vbOKOnly Or vbExclamation End If End Sub Private Sub cmdGetFilename_Click() GetFilenameFromClass txtClass.Text End Sub

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