help required with nsoutlineview reload feature

Hi guys
I am trying to build a cocoa app which shows directory contents like explorer view of windows. to do this i used NSOutlineview on the left and a NSTableview to its right. now whenever i select an item from the table view and click delete, that file or folder gets deleted from the file system and then table view refreshes itself. Also the table view sends a notification to the outline view so that the outline view can refresh itself. 
So here comes the problem---- my outline view is receiving the notification but it is not reloading the data. Please can you guys suggest me a solution to this problem( struggling on it for past few days now).

Thanks