Option Explicit
 
 
Public Function Addieren(ByVal a As Long, ByVal b As Long) As Long
    On Error Resume Next
    Addieren = a + b
End Function

Option Explicit
 
 
Public sDLL As New A1DLLTest
 
Private Sub Command1_Click()
    On Error GoTo f
 
    With Form1
        .Text1.Text = sDLL.Addition(CLng("1"), CLng("3"))
    End With
    Exit Sub
f:
    MsgBox "f"
    Resume Next