Imports System.IO
Public Class Form1
    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        If Not File.Exists(TextBox1.Text) Then
            MsgBox("Soubor neexistuje!", MsgBoxStyle.Critical, "Chyba")
            Exit Sub
        End If
        soubor = TextBox1.Text
        Me.Hide()
        Worker.Show()
    End Sub
    

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        OpenFileDialog1.ShowDialog()
        TextBox1.Text = OpenFileDialog1.FileName
    End Sub
End Class