vb.net – Limited Multiselect in open file dialog?

I want the user to have the option to select multiple files through openfiledialog which I have in my code, but then if the user selects a file from one folder he is then restricted to select another file only from this specific folder. What is the best way to approach to this problem?

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim openfiledialog1 As New OpenFileDialog
    With openfiledialog1
        .Title = "Select your models"
        .Filter = "Solidworks Files|*.sldprt;"
        .Multiselect = True
    End With
    If OpenFileDialog1.ShowDialog = DialogResult.OK Then
        For Each mfile As String In openfiledialog1.FileNames
'' Add all filenames in a txt file, in a column
    End If
End Sub