Hi, I tried paul example but got some error:

Code:
System.InvalidOperationException was unhandled
  Message="Cross-thread operation not valid: Control 'ListBox1' accessed from a thread other than the thread it was created on."
  Source="System.Windows.Forms"
  StackTrace:
       at System.Windows.Forms.Control.get_Handle()    at System.Windows.Forms.Control.SendMessage(Int32 msg, Int32 wparam, Int32 lparam)    at System.Windows.Forms.ListBox.get_SelectedIndex()    at System.Windows.Forms.ListBox.set_SelectedIndex(Int32 value)    at multithreading.frmMain.Device1() in J:\Aktif VB.net\multithreading\frmMain.vb:line 12    at System.Threading.ThreadHelper.ThreadStart_Context(Object state)    at System.Threading.ExecutionContext.runTryCode(Object userData)    at System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode code, CleanupCode backoutCode, Object userData)    at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)    at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)    at System.Threading.ThreadHelper.ThreadStart()
  InnerException:
the error occur and point me.

vb Code:
  1. ListBox1.SelectedIndex = i