Beispiel:

Option Explicit
 
Private Declare Function GetClassName Lib "user32" Alias _
                        "GetClassNameA" _
                        (ByVal hwnd As Long, _
                         ByVal lpClassName As String, _
                         ByVal nMaxCount As Long) As Long
 
Private Function RunningInIde() As Boolean
'// --------------------------------------------------------
'// Funktion:  |Ermittelt, ob der Quellcode in der IDE
'//            |ausgeführt wird.
'// --------------------------------------------------------
'// Vorauss.:  |Methode muss sich in einer Form befinden,
'//            |wegen 'hWnd'
'// --------------------------------------------------------
'// Rückgabe:  |True bei Ausführung in der IDE, sonst False
'// --------------------------------------------------------
'// Autor:     | Stefan Kulpa
'//            | EDV Innovation & Consulting - Dormagen
'// --------------------------------------------------------
    Const csCLSNAME As String = "ThunderForm"
    Dim sClassName  As String
    Dim lStrLen     As Long
 
    sClassName = String$(260, vbNullChar)
    lStrLen = _
    GetClassName(hwnd, sClassName, Len(sClassName))
    If lStrLen > 0 Then
        sClassName = Left$(sClassName, lStrLen)
        If Len(sClassName) >= Len(csCLSNAME) Then
            RunningInIde = _
            CBool(Left(sClassName, _
                  Len(csCLSNAME)) = csCLSNAME)
        End If
    End If
 
End Function