I don't think that's possible on WMM
Then don't use WMM. Isn't that like, the golden rule of video making? Its a crap program and if you limit yourself to it you'll have crap videos.
Anyway OP, if you can try and get your hands on an actual decent video editor such as Sony Vegas or Camtasia.
Well out of boredom I looked up Sony Vegas, and I found that they have a free trial, I'm going to download it and see how I like it. I won't be able to afford it any time soon, but a free trial is better than nothing :)
Your first time with the program will probably be very confusing.Stick with it, look up tutorials on youtube and it becomes very easy to understand.
This is what came to mind one day when my dad told me to go "straight to bed" when we get home. VideoFeedback is very much appreciated- I wasn't quite sure if the joke was easy to understand or not
Microsoft Bangla Shi Lo-Pow India is a great alternative to Microsoft Sam.