Public Class frmGhostUser
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        If TextBox1.Text <> String.Empty Then
            Dim osql = $"SELECT COALESCE(MAX(GUID),0) FROM TBDD_USER WHERE USERNAME = '{TextBox1.Text}'"
            Dim oUSERID = MyDB_DDECM.GetScalarValue(osql)
            If oUSERID = 0 Then
                MsgBox("Username unbekannt!", MsgBoxStyle.Information)
            Else
                GHOST_USERID = oUSERID
                USER_USERNAME = TextBox1.Text
                Me.Close()
            End If
        End If
    End Sub
End Class