Wait for Backgroundworker to finish

[Cyb3rH4Xter]

How can I wait for a backgroundWorker to finish and still be in the same void?
For example:

I send a list with files to process to a void, DoThem(list).
Then in that void, if the file is a txt, send it to backgroundworker1. If the file is a jpg send it to backgroundworker2.

But I only want one backgroundworker to run at the same time (reporting progress to the same progressbar).

I know the bw has a bwFinished event, but if I need to use that I would need to do a hell of a more programming that looks quite ugly to me (passing a parameter with what to do when finished blablabla).

What I have read you can use the WaitOne thingy. But it locks the UI and I want to be able to change the progressbar all the time.