I have to apologize in advance that this post is going to sound very generic, but I'm home with the family for Thanksgiving and couldn't find the specific info in a quick search.
Somewhere in this HTPC forum I was pointed to a piece of software written by a Microsoft employee as an example of how to program plugins to Media Center. His plugin adds a "jump" capability to any audio/video playing in MCE. It can be used in various ways but the basic controls are something like this:
Press right arrow, enter a time code like "130", press OK -> video jumps 1:30 forwards
Press left arrow, enter a time code like "130", press OK -> video jumps to the 1:30 mark (regardless of if that's a forwards or backwards jump)
I'm not sure if this is anything that you could use, but I do use it regularly for skipping around in DivX/Xvid files, and it's great for the live DJ sets I listen to as well. I stumbled across it while looking for a beter way to FF through 2 hour long .mp3s without rapid-fire pressing "skip".
The only other thing I can think of is changingthe "skip" button to jump ~2 seconds instead of 30, and somehow writing a plugin to allow holding down the button as a rapid-fire rather than a jump to end of file. This sounds more like what you're asking for, but I wouldn't know how to do it.
Anyway, hopefully someone else can fill in the details that I'm missing, or point you to the software I mentioned if you think it will help at all. Good luck!