Since you specified the BlackBerry Browser I'm assuming your company has a BES. In that case you could up the maximum file size, but that just pushes the problem further down. Blackberries have limited Application Memory, so you will probably want to make sure that the videos end up on the SDCard or the Device Memory if equipped (as the 9000 is). You probably don't want to leave this up to the user as they can easily get it wrong and cause you and or IT support grief.
You could do this with a Java program written using either the JDE
or Eclipse with the BlackbBerry plugin
if you have the OS to support that.