Handling Mouse Events

Yes I used mouse leave event. But it didn't work for me. Actually it works but it did not work like that as I wish. I use mouse Enter and mouse move events for "open" toolstripmenuitem. It shows description in label "Open files" But when I leave "open" toolstripmenuitem. Label remains unchanged. Label changes when any control in focus on the form. I can't understand working of mouse leave event or when this event fires. Please give me an example code to help me in understanding these events. Thanks for replying my question. Here is my code

private void openToolStripMenuItem_MouseEnter(object sender, EventArgs e)
{
         label1.Text =  "Open files";

}


private void openToolStripMenuItem_MouseLeave(object sender, EventArgs e)
{
         label1.Text = "";

}