If Suchbegriff1.Value = "" Then
    sql = "SELECT [In 2002].Vorname, [In 2002].Familienname, [In" & _
      "2002].[e-mail], [In 2002].Heimatuni " & _
            "FROM [In 2002];"
     GoTo Abfrage_durchführen
Else
    sql = "SELECT [In 2002].Vorname, [In 2002].Familienname, [In" & _
      "2002].[e-mail], [In 2002].Heimatuni " & _
              "FROM [In 2002] " & _
              "WHERE ([In 2002]." & Feld1.Value & "=""" & Suchbegriff1.Value & _
              """)"
End If