Controling the Mediaplayer

I´ve created a small dialogbased app that has a fileopen-button and a few
mediaplayer control buttons such as play, stop and pause. I have also
created a dialog that contains the activex- component Mediaplayer. When
selecting a file in the fileopen dialog I have made it show the
mediaplayerdialog. I´ve created this dialog modless so that I can control it
using the buttons in the parentdialog. The problem I have now is how do i
send the opened file to the mediaplayer so that it can start to autoplay? I
also want it to check the imagesize of the file and make the playingdialogs
size after that.

Any hints would be great

Frederik