Public Class WebRipper : Inherits BackgroundWorker

    Dim Index As Integer
    Sub New(SessionId As Integer)
        Index = SessionId
    End Sub

    Sub Start(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles Me.DoWork
		Dim tst = sender.TextBox1.Text
		Dim p As New ProcessStartInfo
		p.FileName = "RunProject.exe"
		p.Arguments = "Process.exe -password_id " + Form1.TextBox1.Text '<= ПРОБЛЕМА ЗДЕСЬ! Не получается обратиться к Form1!
		Dim aroras As Process = Process.Start(p)
		aroras.WaitForExit()
    End Sub

    Private Sub Finish(sender As WebRipper, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles Me.RunWorkerCompleted
        Me.RunWorkerAsync()
    End Sub

End Class

Public Class Form1
    Dim ThreadNum = 10
    Public WR(ThreadNum) As WebRipper
    Dim Started As DateTime

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        For i As Integer = 0 To ThreadNum - 1
            WR(i) = New WebRipper(i)
            WR(i).RunWorkerAsync()
        Next
    End Sub

    Sub WRCompleted(sender As WebRipper, e As System.ComponentModel.RunWorkerCompletedEventArgs)
        sender.RunWorkerAsync()
    End Sub

End Class

Form1.TextBox1.Text