custom progress bar in a datagridview with threading

I am creating a program similar to a download manager. In my form(DownloadManagerForm.cs) I already created a datagridview with a custom progress bar(i found out i have to create classes called DataGridViewProgressColumn and DataGridViewProgressCell because datagridview does not support other controls). In my other class (BHO) i have to activate the DownloadManagerForm automatically and use a thread so it can facilitate multiple downloading. I used the Invoke method and a certain Callback. I noticed that when i run the program the progress bar starts with 0 then 100.I want to see the progress bar move slowly or at least see it move somehow. Please tell me what to add with my code.. Thanks

 columnGraphics = new DataGridViewProgressColumn();
  dataGridView1.Rows.Add(columnGraphics);
            thrDownload = new Thread(Download);
            thrDownload.Start();
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Download()
{
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 this.Invoke(new UpdateProgessCallback(this.UpdateProgress), new object[] { strLocal.Length, fileSize });
}

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UpdateProgress
{
  int PercentProgress = Convert.ToInt32((BytesRead * 100) / TotalBytes);
  updatedProgress = ((float)PercentProgress);
  Graphics.CellTemplate.Value = updatedProgress;
}
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Class
DataGridViewProgressColumn and DataGridViewProgressCell