i know the code to use.... but im not so sure how to make it finish when your File finishes updating.
progressbar1.Maximum = 5; //maximum value for the progress bar.
progressbar1.Minimum = 0; //Minimum value for the progress bar.
progressbar1.Step = 1; //progress bar value increment for every step.
Then in some other part of your code.. say Timer1_Tick put
progressbar1.Value =+ 1; //Increases the step by 1
so that after 5 ticks of the timer.. the progress bar is done, This is only an example, i hope it helps a little bit with relevance to file progress.