Option Explicit

Private Declare Function SendMessage Lib "user32" Alias _
      "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _
      ByVal wParam As Long, lParam As Any) As Long

Private Const LB_GETSELCOUNT = &H190
Private Const LB_GETSELITEMS = &H191

Private Sub Form_Load()
  Dim n As Integer

  For n = 1 To 100
    List1.AddItem "Eintrag " & CStr(n)
  Next
End Sub

Private Sub cmdDelete_Click()
  Dim nSelCount   As Long
  Dim aIndexes()  As Long
  Dim n           As Long

  With List1
    nSelCount = SendMessage(.hwnd, LB_GETSELCOUNT, 0, 0)

    If nSelCount > 0 Then
      ReDim aIndexes(nSelCount - 1)
      SendMessage .hwnd, LB_GETSELITEMS, nSelCount, aIndexes(0)

      For n = UBound(aIndexes) To 0 Step -1
        .RemoveItem aIndexes(n)
      Next

      Erase aIndexes()

    Else
      MsgBox "Es sind keine Einträge zum Löschen markiert!", _
                  vbOKOnly, Title:="VB-fun-Demo"
    End If
  End With
End Sub