Need to trigger an event in windows form program

I already have code that runs when a user leaves a textbox to set properties based on the text entered.  I recently added code to import a lot of the data that the user would have entered manually before. That means that the Leave event on that text box never triggers.

I thought I could use RaiseEvent(), but my program does not recognize it. I do have
"using System.Windows.Forms;"

I'm using Visual Studio 2005.