Ok so I remember catching the tail end of a movie years ago ( early 2000s )so I don't remember much about the movie but I would like to see it, it was a suspense type movie where two kids ( I believe a girl and her little brother) were locked in their house because their dad wealthy I believe, and the guy who locked them in the house wanted something from their dad, and all I know is at the end they escaped by crawling through a vent, I know this is a horrible vague description but maybe some one can help

I believe you are describing a movie called, "Hostage". It was released in 2005, starring Bruce Willis, Kevin Pollak, Ben Foster.

Also, if you have Satellite or cable with a subscription to HD channels, that movie will be shown on October 29, 2011 on Universal HD channel @ 5:00PM EDT. It will repeat on the following morning @ 3:00AM EDT on the same channel.